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GIFT  OF 

PROF.  w.B.  RISING 


s,  and 


stack. 

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R. 


rol. 
IS. 

s., 


A.M., 


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ond.,) 


Poly 


tiools, 
H. 
ilfour, 


20.  N AV  IUH.  I  iuis .     J5y  iienry  rweib,  L,L,.U.,  iiyuiuum. 

21.  NAUTICAL  ASTRONOMY.     By  Henry  Evers,  LL.D. 

22A  STEAM  AND  THE  STEAM  ENGINE— LAND  AND   MARINE. 

By  Henry  Evers,  LL.D.,  Plymouth. 
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Evers,  LL.D.,  Plymouth. 
83.  PHYSICAL  GEOGRAPHY.     By  John  Macturk,  F.R.GS. 

24.  PRACTICAL  CHEMISTRY.     By  John  Howard,  Loacon. 

25.  ASTRONOMY.     By  J.  J.  Plummer,  Observatory,  Durham. 


IN    COURSE    OP    PUBLICATION. 


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.    MACHINE     CONSTRUCTION     AND     DRAWING.       ^7  E. 

Tomkins,  Queen's  College,  Liverpool.    2  vols.  :  Vol.  I,  Text;  Vol.  II,  Plates. 

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of  Natural  Philosophy,  Edinburgh. 

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College,  Manchester. 

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Derby. 

9.  MAGNETISM    AND    ELECTRICITY.     By    F.    Guthrie,    B.A., 

Ph.D.,  Royal  School  of  Mines,  London. 

10.  INORGANIC  CHEMISTRY.     By  T.  E.Thorpe,  Ph.D.,  F.R.S.E. 

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Glasgow  University. 

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of  Anatomy  and  Physiology,  Galway. 

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20.  NAVIGATION.     By  Henry  Evers,    LL.D.,  Professor   of  Applied 

Mechanics,  Plymouth. 

21.  NAUTICAL  ASTRONOMY.     By  Henry  Evers,  LL.D.,  Plymouth. 

22.  STEAM  AND  THE  STEAM  ENGINE—  LAND,  MARINE,  AND 

LOCOMOTIVE.     By  Henry  Evers,  LL.D.,  Plymouth. 

23.  PHYSICAL  GEOGRAPHY.     By  John  Young,  M.D.,  Professor  of 

Natural  History,  Glasgow  University. 


^ 


LECTURE    NOTES 


QUALITATIVE  ANALYSIS. 


HENRY  B.  HILL,  A.M., 

Assistant  Professor  of  Chemistry  in  Harvard  University. 


NEW  YORK : 
G.   P.   PUTNAM'S   SONS. 

1874. 


PREFACE. 


ALTHOUGH  the  advantages  to  be  gained  by  teaching  qualitative 
analysis  by  lecture  are  sufficiently  obvious,  it  is  a  serious  disadvantage 
to  the  student  that  the  necessity  of  taking  proper  notes  often  pre- 
vents him  from  seeing  what  takes  place  upon  the  lecture  table.  This 
little  book  was  intended  to  give  concisely  the  most  important  facts 
essential  to  intelligent  work  in  the  laboratory,  and  thus  give  the  stu- 
dent more  leisure  for  observation  in  the  lecture  room. 

A  comparative  description  of  those  compounds  of  bases  and  acids 
which  are  commonly  found  or  used  in  analysis  is  first  given,  and  after- 
wards a  method  of  separation  which  experience  has  proved  to  be  suf- 
ficiently simple  and  accurate,  is  briefly  explained.  This  method  of 
procedure  from  the  properties  of  compounds  to  the  methods  of  sepa- 
ration will  also  serve  to  show  the  way  in  which  the  more  difficult 
problems  of  analysis  must  be  solved. 

No  tables  for  analysis  have  been  given,  since  their  use  is  of  ques- 
tionable advisability,  and,  if  used,  are  much  better  drawn  up  by  the 
student  himself. 

Symbols  have  been  used  throughout  for  reagents  for  the  sake  of 
brevity,  those  used  in  solution  being  distinguished  by  the  addition 
of  "Aq." 

For  the  sake  of  simplicity,  water  has  often  been  omitted  from  the 
formulae  of  compounds,  inasmuch  as  the  number  of  molecules  of  water 

237570 


iv  PREFACE. 

is  largely  dependent  upon  circumstances,  and  its  presence  is  of  minor 
importance. 

Of  a  compilation  of  this  sort,  it  is  hardly  necessary  to  add  that 
its  facts  are  taken  mainly  from  the  text-books  of  Fresenius  and  Rose, 
and  the  Dictionary  of  Solubilities  of  Storer. 

CAMBRIDGE,  Sept  i,  1874. 


INTRODUCTION. 


QUALITATIVE  ANALYSIS  is  that  branch  of  chemistry  which  treats  of 
the  recognition  of  elements  or  their  compounds.  It  demands  a  thor- 
ough study  and  comparison  of  the  several  elements  and  their  com- 
pounds, of  the  phenomena  exhibited  by  them  under  various  conditions, 
and  the  determination  of  the  particular  conditions  essential  to  the 
manifestation  of  each.  It  is  advisable,  at  first,  to  take  into  consider- 
ation only  the  more  common  compounds,  and  to  leave  for  subsequent 
study  all  rare  elements  and  all  but  a  few  of  the  compounds  of  carbon 
(organic  substances). 

The  phenomena  exhibited  by  a  substance  under  various  conditions 
are  termed  its  reactions.  The  conditions  under  which  reactions  are 
studied  may  be  divided  into  two  classes  :  those  dependent  upon  solu- 
tion, and  those  independent  of  it ;  the  two  modes  of  examination  are 
known  as  the  wet  and  the  dry  way.  In  either  case  any  known  sub- 
stance which  is  used  in  effecting  a  reaction  is  called  a  reagent. 

Reactions  in  the  dry  way  are  dependent  upon  volatilization,  or 
chemical  change  effected  by  heat.  The  nature  of  these  changes  will 
be  sufficiently  clear  after  a  study  of  the  reactions  described  in  the  pre- 
liminary examination. 

In  the  wet  way  a  reagent  is  used  to  effect  solution  or  to  determine 
a  metathesis.  Experience  has  shown  that  when  the  solutions  of  two 
substances  are  mixed,  and  a  compound  insoluble  under  the  existing 
conditions  can  be  formed  by  metathesis,  that  this  insoluble  compound 
is  formed  ;  or  when  a  substance  volatile  under  the  existing  conditions 
can  be  formed,  that  it  is  formed  and  escapes.  An  insoluble  substance 


VI  INTRODUCTION. 

separating  from  solution  is  called  a  precipitate.  If  the  precipitate 
settles  readily,  the  liquid  may  be  decanted,  or,  in  any  case,  it  may  be 
separated  by  filtration,  when  the  liquid  is  called  the  filtrate.  Inas- 
much as  the  completeness  of  the  separation  of  those  subst an ces  which 
are  precipitated  by  a  reagent  from  those  which  are  left  in  solution 
depends  upon  the  insolubility  of  the  precipitate,  all  the  conditions 
which  may  affect  its  solubility  must  be  known  and  considered. 

A  general  reagent  is  used  to  precipitate  a  number  of  substances, 
a  special  reagent  as  a  test  for  a  single  substance.  Some  special  re- 
agents give  no  precipitate,  but  cause  a  change  of  color.  The  precip- 
itate thrown  down  by  a  general  reagent  always  requires  further  ex- 
amination, and  it  is  better  to  submit  to  a  confirmatory  test  the  pre- 
cipitate caused  by  a  special  reagent.  A  precipitate  or  reaction  is  said 
to  be  characteristic  when  no  further  test  is  needed. 

There  are  two  things  essential  to  success  in -qualitative  analysis, 
the  accurate  observation  of  phenomena  and  a  correct  interpretation 
of  their  significance,  neither  of  which  can  be  attained  without  con- 
scientious work  in  the  laboratory.  By  studying  the  reactions  of 
known  substances,  taking  care  to  observe  everything  which  takes 
place,  however  small  it  may  seem,  the  power  of  observation  will  be 
educated,  and  it  will  soon  be  possible  to  determine  what  is  acci- 
dental and  what  essential,  and  experience  will  show  what  is  the 
meaning  of  each  reaction  observed. 

In  this  book  it  is  supposed  that  the  student  already  has  a  good 
knowledge  of  general  chemistry.  Such  knowledge  is  essential,  and 
may  be  gained  by  the  aid  of  any  good  text-book  on  chemistry. 
Experience  in  laboratory  work  and  manipulation,  though  not  abso- 
lutely necessary,  is  on  all  accounts  desirable.* 

It  is  best  to  begin  with  the  study  of  the  bases,  and,  taking  each 
group  by  itself,  to  compare  the  properties  of  the  different  members. 
The  description  of  the  properties  of  bases  is  intended  as  a  guide 

*  The  student  may  be  referred  to  the  following  text-books  :  — 
PRINCIPLES  OF  CHEMICAL  PHILOSOPHY.     By  Josiah  P.  Cooke,  Jr.     Boston,  1874. 
A  MANUAL  OF  INORGANIC  CHEMISTRY  :  Arranged  to  facilitate  the  Experimental 

Demonstration  of  the  Facts  and  Principles  of  the  Science.     By  C.  W.  Eliot  and 

F.  H.  Storer.     New  Yqrk,  1868. 
INORGANIC  CHEMISTRY.     By  T.  E.  Thorpe.     New  York,  1874. 


INTRODUCTION.  Vll 

in  this  work.  The  truth  of  each  important  fact  given  there  should 
be  experimentally  proved,  and  reactions  seen  in  the  lecture-room 
should  be  repeated,  if  possible. 

After  a  thorough  study  of  the  properties  of  a  group  of  bases,  a 
method  of  separation  should  be  devised  and  compared  with  that 
given  in  course  of  analysis.  The  members  of  the  group  must  then 
be  separated  from  each  other,  taking  care  that  the  facts  upon  which 
the  method  of  separation  is  based  are  well  understood,  and  the 
sources  of  error  distinctly  recognized.  The  separation  of  the  group 
as  a  whole  from  the  other  groups  must  then  be  considered,  and  the 
conditions  necessary  for  complete  separation  clearly  made  out. 
After  the  basic  groups  have  been  studied  in  order,  and  each  of  the 
bases  can  be  detected  with  certainty,  a  similar  method  should  be 
followed  with  acids,  taking  as  a  guide  the  description  of  the 
properties  of  acids,  and  the  methods  given  for  their  detection. 

The  student  will  then  be  prepared  to  make  complete  analyses. 
He  should  begin  with  simple  salts,  and  proceed  gradually  to  com- 
plex mixtures  and  insoluble  substances,  in  every  case  proving  the 
presence  or  absence  of  each  base  and  acid  which  he  has  studied. 
In  the  analysis  of  such  compounds  the  reactions  in  the  dry  way 
should  first  be  observed.  Here  the  significance  of  each  reaction 
may  be  learned,  as  before,  by  practice  upon  known  substances,  or 
the  reactions  of  a  substance  may  be  carefully  observed,,  and  its  com- 
position afterward  determined  by  analysis  in  the  wet  way.  The 
correct  interpretation  of  reactions  in  the  preliminary  examination 
requires  long  practice.  Great  care  must  be  taken  to  distinguish 
between  those  reactions  which  are  so  decisive  that  they  may  be 
taken  as  tests  for  the  presence  or v  absence  of  certain  substances, 
and  those  which  are  proofs  or  indications  of  presence,  if  observed, 
but  from  whose  non-appearance  no  negative  conclusions  can  be 
drawn. 

As  far  as  practical  work  is  concerned,  it  will  be  necessary  to 
give  here  only  a  few  general  directions,  and  point  out  a  few 
common  errors.  Neatness  and  cleanliness  are  absolutely  neces- 
sary. The  reagents  must  be  carefully  preserved  from  contamina- 
tion. The  stoppers  of  the  bottles  must  not  be  misplaced,  nor 
laid  down  while  the  reagent  is  used.  The  reagent  bottles  should 


Vlll  INTRODUCTION. 

be  kept  clean  and  plainly  labelled,  they  should  be  conveniently 
arranged,  and  the  order  of  arrangement  never  changed. 

The  quantity  of  a  substance  taken  for  analysis  should  be  small. 
This  facilitates  the  manipulation,  and  unless  carried  to  extreme, 
affords  better  practice. 

Each  reagent  must  be  added  cautiously,  in  quantity  just  sufficient. 
Too  little  fails  to  effect  complete  precipitation,  and  separation  ;  too 
much  is  often  quite  as  objectionable.  If  the  first  few  drops  of  a 
reagent  cause  a  precipitate,  more  must  be  added  until  a  drop 
allowed  to  run  into  the  solution  gives  no  further  precipitate.  The 
filtrate  should  also  be  tested  with  a  few  drops  of  the  reagent  in 
confirmation.  In  using  an  acid  or  an  alkaline  solution  the  reaction 
on  test-paper  will  show  when  an  excess  has  been  added.  In  the 
use  of  a  few  reagents  the  necessary  quantity  can  be  learned  by  ex- 
perience alone.  In  any  case,  the  reagent  must  be  thoroughly  mixed 
with  the  solution  by  shaking  or  stirring. 

If  a  solution  is  moderately  concentrated,  the  precipitation  is  usually 
immediate  ;  but  in  dilute  solutions  it  often  takes  place  only  after  some 
time.  If  separation  is  to  be  effected,  time  should  be  allowed  for  com- 
plete precipitation.  Occasionally  half  an  hour,  or  even  several  hours, 
are  necessary  ;  but  more  frequently  five  or  ten  minutes  will  be  found 
sufficient.  Heat  almost  always  facilitates  precipitation ;  in  a  few 
cases,  however,  which  are  mentioned  in  the  course  of  analysis,  a  re- 
agent must  be  used  in  the  cold. 

In  filtering,  the  filter  must  be  evenly  folded  and  carefully  fitted  to 
the  funnel.  For  rapid  filtration  a  creased  or  star  filter  is  better,  and 
in  any  case  a  hot  solution  filters  more  rapidly.  Precipitates  must  be 
thoroughly  washed,  though  only  the  first  part  of  the  wash  water 
should  be  saved  with  the  filtrate.  If  the  precipitate  is  granular  and 
settles  readily,  it  may  be  advantageously  washed  by  decantation  before 
it  is  collected  on  a  filter.  A  precipitate  may  be  removed  from  the 
filter  with  a  small  spatula,  or  by  washing  it  off  with  a  stream  of 
water,  and  removing  by  decantation  most  of  the  water.  A  precipi- 
tate may  be  readily  dried  by  supporting  the  filter  over  a  hot  sand-bath, 
either  in  the  funnel  or  on  a  triangle. 

In  fusions  the  well-dried  substances  should  be  intimately  mixed  in  a 
mortar  ;  the  crucible  containing  the  mixture  should  be  supported  just 


INTRODUCTION.  IX 

above  the  point  of  the  blue  cone  of  the  lamp  flame.  The  removal  of 
the  fused  mass  from  a  platinum  crucible  is  much  facilitated  by  setting 
it,  while  cooling,  upon  a  thick,  cold  bit  of  metal. 

In  blowpipe  work  full  time  must  be  allowed  for  reduction  on  char- 
coal. With  borax  but  little  substance  must  be  used,  and  care  must  be 
taken  to  get  a  good  oxidizing  or  reducing  flame,  as  the  case  may  be. 

It  is  essential  that  concise  and  accurate  notes  should  be  kept  of 
all  laboratory  work.  They  should  record  the  reactions,  the  condi- 
tions under  which  they  take  place,  and  the  conclusions  drawn  from 
them.  In  other  words,  they  should  give  in  order  what  is  done,  what 
is  observed,  and  what  is  inferred.  These  notes  should  be  taken  as  the 
work  is  done,  and  are  of  value  only  as  they  are  a  truthful  record  of 
fact. 


CONTENTS. 


PAGE 

Introduction v 

Table  showing  Division  of  Bases  into  Groups I 

Properties  of  Bases 2 

Group  1 2 

Group  II 3 

Group  III... 5 

Group  IV 6 

Group  V 9 

Group  VI 13 

Table  showing  Division  of  Acids  into  Groups 15 

Properties  of  Acids 16 

Group  I 16 

Group  II 22 

Group  III 24 

Preliminary  Examination 25 

Reactions  in  closed  Tube. 25 

"        on  Charcoal 27 

"        with  Borax 28 

Flame  Colors 29 

Examination  with  H2SO4 29 

Treatment  with  Water 30 

"           "     Acids 31 


Xll  CONTENTS. 

PAGB 

Treatment  of  Insolubles 32 

Detection  of  Bases 34 

Group  1 44 

Group  II 42 

Group  III 38 

Group  IV 38 

Group  V 35 

Group  VI 35 

Detection  of  Acids 45 

Group  1 46 

Group  II 50 

Group  III 52 


QUALITATIVE  ANALYSIS. 


BASES. 

GROUP  I 

Sulphides  and  carbonates  soluble  : 

NaJC,  L^JJ^N,  Cs,  Rb. 

GROUP  H. 

Sulphides  soluble,  carbonates  insoluble  : 
Ba,  Sr,  fe  Mg. 

GROUP  III. 

Sulphides  not  formed  in  wet  way.  (H4N)2S  +  Aq  pre- 
cipitates hydrates  : 

Ala,  Cr2,  Tli,  Zr,  G,  Y,  E,  Ce,  La,  D,  Cb,  Ta. 

GROUP  IV. 

Sulphides  not  formed  in  acid  solutions,  but  precipi- 
tated in  alkaline  : 

Fe,  Fe,*,  Ni,  Co,  Mn,^  U,  V,  Te,  In. 

GROUP  V. 

Sulphides   formed   in   acid   solutions,  insoluble  in  al- 
kaline : 

Ag,  Hg,  Hgjf  Pb,  Cu,  Cd?  Bi,  Rh,  Os,  Ru,  Pd. 

GROUP  VI. 

Sulphides  formed  in  acid  solutions,  soluble  in  alkaline  : 
As,  Sb,  Sn,  SnIV,  Au,  Pt,  Ir,  W,  Mo,  Te,  Se. 

*  Is  precipitated  as  Fe  S. 


LECTURE 'NOTES   ON 


PROPERTIES  OF  BASES. 

GROUP  I.    Ha,  K,  Li,  ILN. 

Metals. — Na,  K,  Li.  Soft,  very  fusible,  and  lighter 
than  water.  Oxidize  rapidly  in  air,  or  in  water  setting 
free  H2.  H4N.  Known  only  in  combination,  as  it  is 
decomposed,  when  set  free,  into  2NH;{  and  H.,. 

Oxides. — Na2O  and  K2O  absorb  water  eagerly  from 
the  air,  Li./)  unites  with  water  rca  lily,  (I  I,N"),.O  unknown. 

Hydrates. — NaOH  and  KOH  are  deliquescent, 
LiOH  sparingly  soluble,  and  H4NOH  known  only  in  solu- 
tion. 

Sulphides.— All  soluble. 

Chlorides. — LiCl  is  deliquescent,  the  rest  readily 
soluble.  K4PtCl6  and  (H4N)2PtCl6  are  quite  insoluble  in 
water,  or  HCl-f-Aq,  more  insoluble  in  alcohol.  The 
other  double  chlorides  with  Pt  are  soluble. 

Carbonates. — Li2CO3  sparingly  soluble,  the  other 
neutral  carbonates  readily  soluble,  K.2CO3  deliquescent. 

KHCO3  and  NaHCO3  are  less  soluble  than  the  neu- 
tral salts,  LiHCO3  more  soluble. 

Sulphates. — Na.,SO4,  (H4N),SO4  and  Li,SO4  very  sol- 
uble, K.2SO4  less  so.  The  acid  salts  of  the  form  MHSO4 
are  all  more  soluble  than  the  neutral. 

Chromates. — All  soluble.  The  salts  of  the  form 
M2CrO4  give  "a  yellow  solution,  of  the  form  M2Cr,,O7  a  red. 

Phosphates. — All  Na,  K  and  H4N  salts  soluble. 
Na2HPO4  +  Aq  precipitates  Li3PO4  insoluble  in  water, 
quite  soluble  in  H4NCl+Aq,  and  soluble  in  acids. 

Oxalates. — All  soluble,  KHC2O4  not  readily. 


QUALITATIVE   ANALYSIS.  3 

Tartrates. — Salts  of  the  form  M2C4H4O6  all  sol- 
uble. KHC4H4O6  and  H4NHC4H4O6  are  sparingly  sol- 
uble in  cold  water.  HC2H3O2  does  not  increase  the  sol- 
ubility, though  they  are  soluble  in  mineral  acids,  or  in  an 
alkaline  solution.  The  other  acid  salts  readily  soluble. 

Cyanides. — Soluble  in  water,  the  salts  readily  de- 
composed in  solution. 

Ferrocyanides. — All  soluble. 


GROUP  II.    Ba,Sr,  Ca,  Mg. 

Metals.— Harder  than  metals  of  Gr.  I.  Ba,  Sr,  and 
Ca  oxidize  rapidly  in  air  or  water,  Mg  slowly  in  moist 
air,  or  water  at  100°. 

Oxides. — Combine  with  water  to  form  hydrates. 

Hydrates. — BaO2H2  is  soluble,  SrO2H2  less  so ; 
CaO2H2  sparingly  soluble,  and  the  solubility  decreased 
by  heat.  MgO2H2  is  insoluble  in  water,  though  soluble 
in  solutions  of  H4N  salts.  All  are  readily  soluble  in  acids. 
NaOH  -f  Aq  precipitates  the  hydrates  of  the'  group  ;  Ba, 
Sr  and  Ca  hydrates  only  from  concentrated  solutions. 
H4NOH  +  Aq  precipitates  only  MgO2H2,  that  partially, 
or  not  at  all,  in  presence  of  H4NC1. 

Sulphides.— BaS,  SrS  and  CaS  are  soluble;  MgS  de- 
composes water,  and  therefore  is  not  formed  in  the  wet 
way. 

Chlorides.— BaCl2  and  SrCl.2  readily  soluble,  CaCl2 
and  MgCl2  deliquescent.  MgCl2  in  solution  is  partially 
decomposed  by  evaporation  to  dryness. 

Carbonates. — Carbonates  of  the  form  M"CO3  insol- 
uble in  water,  soluble  in  acids.  CaCO3  and  SrCO3  are 


4  LECTURE  NOTES   ON 

slightly  soluble  in  H4NC1  +  Aq,  BaCO3  more  markedly, 
MgCO3  readily.  Na2CO3  4-  Aq  precipitates  Ba,  Sr  and  Ca 
as  carbonates,  Mg  as  basic  carbonate.  (H4N).2CO3  -f  Aq 
precipitates  Ba,  Sr  and  Ca  completely,  Mg  partially  in  con- 
centrated solutions,  or  not  at  all  in  presence  of  H4NC1. 
The  salts  of  the  form  M"H8  (CO3)2  are  soluble  ;  on  boiling 
their  solutions  the  neutral  carbonates  are  precipitated. 

Sulphates.— BaSO4  and  SrSO4  are  insoluble,  CaSO4 
sparingly  soluble  in  cold  water,  less  in  hot,  MgSO4  readily 
soluble.  Mineral  acids  increase  the  solubility  of  BaSO4 
but  slightly,  of  SrSO4  and  CaSO4  very  decidedly.  In 
strong  H2SO4  all  these  are  soluble,  forming  acid  salts 
M"H«(SO4)fli  decomposed  by  water  with  formation  of 
M"SO4. 

Chromate's. — BaCrO4  insoluble  in  water  or  HC.2USO^ 
soluble  in  HC1  -f  Aq  or  HNO3.  SrCrO4  quite  soluble  in 
water,  readily  in  HC2H3O2,  CaCrO4  and  MgCrO4  soluble 
in  water. 

Phosphates. — Of  the  three  classes  of  phosphaTes^ 
those  of  the  form  M"3(PO4).2  are  insoluble ;  those  of  the 
form  M"2H2(PO4)2  are  practically  insoluble  in  water,  though 
the  Ba  and  Sr  salts  are  markedly  soluble  and  the  Ca  salt 
somewhat  soluble  in  H4NC1  -f  Aq.  The  salts  of  the  form 
M"H4(PO4)j  are  soluble  in  water.  The  insoluble  salts 
are  soluble  in  acids.  In  neutral  solution  Na.2HPO4  -f- 
Aq  precipitates  phosphates  of  the  form  M"SH2(PO4)2,  in 
an  H4NOH  solution  Ba,  Sr  and  Ca  precipitated  in  the 
form  M"3(PO4)2.  Mg  is  precipitated  by  Na8HPO4  -f  Aq 
in  presence  of  H4NC1  and  H4NOH  as  Mg,(H4N).2(PO4),, 
insoluble  in  water,  though  soluble  in  acids. 

Oxalates. — Neutral  oxalates  of  the  form  M"C2O4  in- 


QUALITATIVE   ANALYSIS.  5 

soluble  in  water,  soluble  in  mineral  acids ;  MgC2O4  is 
soluble  in  H4NC1  +  Aq. 

Tartrates. — Neutral  salts  of  Ba.  Sr  and  Ca  insoluble 
in  water,  soluble  in  mineral  acids,  or  NaOH-f  Aq;  more 
or  less  soluble  in  H4NCl  +  Aq.  MgC4H4O6  sparingly 
soluble  in  water,  readily  soluble  in  H4NC1  + Aq. 

Cyanides. — Soluble  in  water,  the  solutions  decom- 
posed by  heat. 

Ferrocyanides. — Ba2Fe(CN)6  sparingly  soluble,  the 
rest  soluble. 

GROUP  HI  AL,  Cr2. 

Metals. — Al  white,  ductile,  fusible,  and  does  not 
readily  oxidize.  It  is  soluble  in  HCl  +  Aq,  in  dilute 
H2SO4,  or  in  NaOH,  +  Aq  with  difficulty  in  HNO3. 
Cr  very  hard  and  infusible. 

Oxides. — Insoluble  in  water;  before  ignition  they 
are  soluble  in  acids,  after  ignition  insoluble.  Fusion 
with  Na2CO3  and  KNO3  converts  A12O3  into  soluble 
Na6O6Al,,  and  Cr2O3  into  Na2CrO4. 

Hydrates. — Insoluble  in  water,  soluble  in  acids,  or 
NaOH-j-Aq.  Cr3  precipitated  from  NaOH  solution  by 
boiling  as  Cr8O6H6,  A12  is  not.  Both  slightly  soluble  in 
H4NOH  +  Aq,  the  solubility  of  AloO6H6  diminished  by 
presence  of  H4NCL  On  heating  the  solution  the  dis- 
solved hydrates  are  precipitated. 

Sulphides. — Not  formed  in  the  wet  way  A1.2S3  decom- 
poses water,  liberating  H.,S  and  forming  Al^H^. 
(H4N),S  +  Aq  precipitates  A12O6H6  and  CraO6H«  with 
evolution  of  HaS.1 

1  (AlaCle  +  3(H4N2)S  +  6H20  +  Aq)  = 

+  (6H4NC1+  Aq). 


0  LECTURE  NOTES   ON 

Chlorides.— Soluble,  Al.Cle  deliquescent. 

Carbonates.— Normal  salts  unknown.    Na.2CO3 
or   (H4N)2CO3-}-Aq  precipitate  essentially  A1,,O6H6  and 
Cr,O6H6  with  escape  of  CO2.' 

Sulphates. — Soluble.  Most  commonly  found  with 
K2SO4  as  alums. 

Phosphates.— Salts  of  the  form  (M,)VIH1,(PO4)ti  are 
soluble,  the  other  phosphates  insoluble  in  water,  soluble 
in  acids  or  NaOH  +  Aq;  the  Cr2  salts  precipitated  on 
boiling  the  NaOH  solution. 

Oxalates. — The  normal  A12  salt  insoluble,  the  Cr2  salt 
soluble. 

Tartr at es.— Readily  soluble  in  water.  From  their 
solutions  A12O6H6  and  Cr^OgHe  cannot  be  precipitated. 

Cyanides. — Cr,(CNj6  insoluble  in  water,  slowly  solu- 
ble in  KCN  +  Aq. 

GROUP  IV.    Fe,  Ni,  Co,  Mn,  Zn. 

Metals. — Fe,  Ni,  Co,  Mn,  hard,  fuse  only  at  high 
temperatures,  Zn  soft,  readily  fusible,  boils  at  red  heat. 
Mn  and  Fe  oxidize  readily  in  moist  air,  Co  and  Ni  do  not. 
All  soluble  in  acids. 

Oxides. — All  insoluble  in  water,  soluble  in  acids, 
though  FeO  and  FesO8  dissolve  very  slowly  after  igni- 
tion. MnO2  dissolves  in  HCl-f-Agwith  evolution  of 

a  2 
2' 

Hydrates. — Insoluble  in  water,  soluble  in  acids. 
FeO2H.2,  white,  rapidly  turning  green  or  black,  and  MnO4H2, 

1  (Al2Cl6  +  3Na2CO3  +  3H.2O  +  Aq)  = 

Al.O6H6  +  3CO2  +  (6NaCl  +  Aq). 

2  (MnOa  +  4HCl  +  Aq)  =  (MnCl4  +  2H2O  +  Aq).      The  solution 
then  gently  heated ;   (MnCl4-f  Aq)—  (MnCla  +  Aq)  +  Cl2. 


QUALITATIVE  ANALYSIS.  7 

flesh  colored,  turning  brown,  are  soluble  in  H4NCl  +  Aq; 
NiO2Hs,  pale  green,  and  CoO2H2,  pink,  are  soluble  in 
H4NOH-f  Aq  or  H4NC1  +  Aq  ;  ZnO.2H2,  white,  is  soluble 
in  H4NOH  +  Aq,  NaOH  +  Aq  or  H4NC1  +  Aq. 
H4NOH  +  Aq  and  NaOH  +  Aq  precipitate  the  hydrates, 
—  with  Co  a  blue  basic  salt  in  the  cold,  but  the  hydrate 
on  boiling.  Mn8O4Hs,  brown,  Ni2O6H6,  black,  CoO6H6, 
black,  and  Fe2O6H6,  red  brown,  are  insoluble  in  water  or 
H4NCl+Aq,  but  soluble  in  acids. 

Sulphides.  —  Insoluble  in  water  or  in  solutions  of  the 
hydrates  or  sulphides  of  Gr.  I.  When  moist  they  are  oxi- 
dized upon  exposure  to  the  air,  some  of  them,  at  least, 
turning  into  soluble  sulphates.  FeS,  black,  MnS,  flesh  col- 
ored, soluble  in  dilute  acids  ;  ZnS,.  white,  soluble_in  dilute 
mineral  acids,  insoluble  in  HC2H3O2  ;  NiS,  black,  CoS, 
black,  insoluble  in  cold  dilute  acid,  soluble  in  strong  hot 
HCl+Aq  or  HNO3.  The  sulphides  are  not  precipitated 
by  H3S  from  acid,  or,  at  best,  partially  from  neutral  solu- 
tions, except  ZnS,  which  is  precipitated  from  solution  in 
HC2H3O2.  Fe2S3  cannot  be  formed  in  the  wet  way. 
From  solutions  of  Fe2  salts  (H4N)2S-|-Aq  precipitates  FeS 
with  separation  of  S.1  In  acid  solutions  H2S  converts 
Fe2  salts  into  Fe.2  (H4N)2S-f  Aq  precipitates  the  other 
members  as  hydrated  sulphides. 

Chlorides.  —  All  readily  soluble,  ZnCl2  very  deliques- 
cent. 

Carbonates.  —  Neutral  salts  M"CO3  insoluble  in  water, 
soluble  in  acids.  FeCO3  soluble,  MnCO3  slightly  solu- 
ble in  H4NC1+  Aq;  NiCO3  and  CoCO3  are  soluble  in 


(Fe2Cl8  +  3  (H4 

=  S  +  (2FeCla+2HCl+Aq). 


8  LECTURE  NOTES   ON 

H4NCl+Aq  or  H4NOH  +  Aq;  ZnCO3  soluble  in 
NaOH-f-Aq,  H4NCl  +  Aq  or  H4NOH-fAq.  From 
solutions  of  Fe2  salts  soluble  carbonates  precipitate 
essentially  FesO6H6  with  evolution  of  CO2.  From  solu- 
tions containing  other  members  of  the  group  Na^COg  +  Aq 
precipitates  basic  carbonates;  (H4N)2CO3  +  Aq  precipi- 
tates similar  basic  salts,  those  of  Ni,  CO  and  Zn  being 
soluble  in  an  excess. 

Sulphates. — All  readily  soluble. 
Phosphates. — Salts  of  the  form  M"H4  (PO4)3  solu- 
ble, of  the  forms  M"2H2  (PO4)2  and  M"3  (PO4)3  insoluble 
in  water,  soluble  in  acids,  more  or  less  soluble  in  solu- 
tions of  the  soluble  salts  of  the  same  member  of  the 
group.  The  Mn  salts  are  soluble  in  H4NCl  +  Aq; 
the  Ni  and  Co  salts  in  H4NC1  +  Aq  or  H4NOH  +  Aq  ; 
the  Zn  salts  in  H4NCl  +  Aq,  H4NOH  +  Aq  or  NaOH-f 
Aq.  Na.2HPO4  +  Aq  added  in  excess  precipitates  members 
of  the  group  in  the  form  M3  (PO4).:. 

Oxalates. — The  neutral  salts  insoluble  in  water, 
soluble  in  acids.  The  Ni  and  Co  salts  readily  soluble 
in  H4NOH  +  Aq;  ZnC,O4  soluble  in  H4NOH  +  Aq, 
H4NCl  +  Aq  and  NaOH+Aq. 

Tartrates. — ZnC4H4O6  and  NiC4H4O6  insoluble  in 
water,  soluble  in  acids  or  NaOH  +  Aq  ;  MnC4H4O6  and 
FeC4H4O6  sparingly  soluble  in  water,  readily  soluble  in 
NaOH  +  Aq;  CoC4H4O6  and  Fe2(C4H4O6)3  soluble  in 
water,  the  solutions  not  precipitated  by  NaOH  +  Aq,  or 
Na2CO3  +  Aq. 

Cyanides. — With  the  exception  of  the  Fe2  salt,  which 
is  unknown,  the  cyanides  are  all  insoluble  in  water  and 
soluble  in  KCN-f  Aq.  Ni(CN)2  and  Co(CN)9  are  also 


QUALITATIVE  ANALYSIS.  9 

soluble  in  H4NOH  +  Aq,  Zn(CN)2  in  H4NOH  -f  Aq 
or  NaOH  +  Aq.  From  the  solutions  in  KCN  +  Aq 
Ni(CN)2  and  Zn(CN)2  are  reprecipitated  by  neutralizing 
the  KCN  with  acids.  The  solutions  of  the  other  cyan- 
ides in  KCN  +  Aq  contain  (in  the  case  of  Mn-  and  Co 
only  after  heating  or  exposure  to  air)  K4Fe(CN)6, 
K6Mn2(CN)12  and  KeCo2(CN)i2  from  which  acids  do  not 
separate  the  simple  cyanides,  and  from  which  Fe,  Mn 
and  Co  cannot  be  precipitated  by  ordinary  reagents. 

Ferrocyanides. — Insoluble  in  water,  decomposed 
by  NaOH  +  Aq  into  hydrate  of  the  metal,  and 
Na4Fe(CN)6.  Zn2Fe(CN)6,  white,  Ni2Fe(CN)6,  greenish 
white,  Co,Fe(CN)6,  green,  FeK2Fe(CN)6,  white,  rapidly 
turning  blue,  and  (Fe2)2(Fe(CN)6)3,  blue,  insoluble  in 
HCl  +  Aq;  Mn2Fe(CN)6,  reddish  white,  soluble  in 
HC1  +  Aq.  All  are  decomposed  by  heating  with  H2SO4 
diluted  with  ^  its  volume  of  water ;  HCN  evolved, 
and  sulphates  left. 

GROUP  V.    Ag,  Hg,  Pb,  Cu,  Cd,  Bi. 

Metals.— Bi  brittle,  Ag  and  Pb  soft,  Cu  and  Cd  hard- 
er, Hg  liquid  at  ordinary  temperatures.  Exposed  to  the 
air  Ag,  Bi  and  Hg  do  not  oxidize,  Pb,  Cu  and  Cd  not 
readily.  All  but  Ag  oxidize  rapidly  at  high  temperatures. 
HNO3  is  the  best  solvent  for  all,  though  Cd  dissolves 
in  any  acid.  HCl  +  Aq  does  not  act  upon  Ag,  Hg,  Pb, 
or  Bi,  and  acts  upon  Cu  only  in  presence  of  O.  Hot 
concentrated  H.SO4  dissolves  all  but  Pb,  which  it  affects 
but  little. 

Oxides. — AgjO,  brown,  slightly  soluble  in  water,  readi- 
ly soluble  in  H4NOH-h.Aq,  and  in  solutions  of  chlorules, 
cyanides  or  hyposulphites  or  in  HNO3.  HgO,  yellow 


10  LECTURE  NOTES   ON 

or  red,  and  Hg.^0,  black,  insoluble  in  water,  soluble  in 
HNO3.  PbO,  reddish  yellow,  CuO,  black,  Cu,O,  red,  CdO, 
brown,  and  Bi-jOg,  yellow,  in  solubility  are  like  the  hy- 
drates. 

Hydrates. — Ag  and  Hg  form  no  hydrates.  PbO.jH2 
is  practically  insoluble  in  water,  though  alkaline  to  test 
paper,  readily  soluble  in  NaOH-j-Aq.  CuOgH,,  blue,  and 
CuaOaH8,  orange  yellow,  insoluble  in  water,  slightly  solu- 
ble in  cold  NaOH  +  Aq,  soluble  in  H4NCl  +  Aq,  or  in 
H4NOH+Aq.  On  boiling  CuO.H,  with  NaOH-f  Aq 
it  is  converted  into  CuO,  the  small  amount  dissolved  in 
the  cold  being  precipitated  ;  CdO-^Hj,  white,  insoluble  in 
water,  soluble  in  H4NOH-f  Aq;  BiO3H3,  white,  insoluble 
in  water  or  H4NOH+Aq.  All  these  hydrates  readily 
soluble*in  acids. 

From  solutions  containing  members  of  the  group 
NaOH  +  Aq  precipitates  Ag,  Hg  and  Hg2  as  oxides,  the 
rest  as  hydrates,  PbO^H..,  soluble  in  an  excess ; 
H4NOH  +  Aq  precipitates  Ag  as  oxide,  Hg  and  Hg2  as 
insoluble  amine  compounds,  the  rest  as  basic  salts,  or 
hydrates,  the  Ag,  Cu,  and  Cd  precipitates  being  soluble  in 
an  excess. 

Sulphides. — Insoluble  in  water,  cold  dilute  acids  or 
solutions  of  the  hydrates  or  sulphides  of  Gr.  I. ;  allexcept 
HgS  and  Hg,S  soluble  in  hot  dilute  HNO,;.  ifgS,  black, 
Ag.,S,  black,  CuS,  black,  and  Bi.,8;.,  black,  may  be  complete- 
ly precipitated  from  solutions  containing  HC1  -f  Aq, 
unless  present  in  very  great  excess.  PbS,  black,  and  CdS, 
yellow,  are  not  completely  precipitated,  if  much  HC1  -f  Aq 
is  present.  Hg  solutions  are  precipitated  by  H2S  first 
white,  then  yellow,  the  color  changing  to  brown  red,  and 


QUALITATIVE  ANALYSIS.  II 

becoming  black  only  with  excess  of  H2S.  The  change 
of  color  is  due  to  the  formation  of  various  insoluble  com- 
pounds of  HgS  with  undecomposed  Hg  salt. 

Chlorides. — AgCl  insoluble  in  water  or  acids,  soluble 
in  H4NOH-{-Aq  and  in  solutions  of  chlorides, -cyanides 
or  hyposulphites.  Hg2Cl2  insoluble  in  water  but  gradually 
decomposed  by  boiling  with  water,  HC1  +  Aq  or  solutions 
of  chlorides ;  H4NOH  +  Aq  converts  it  into  (Hga)8  H4N2C12, 
black,  insoluble  in  water  or  H4NOH  +  Aq.  PbCl2 
crystalline,  sparingly  soluble  in  cold  water,  still  less  soluble 
in  dilute  HCl-j-Aq,  soluble  in  hot  water,  in  concentrated 
HC1  +  Aq,  or  in  NaOH  4-  Aq.  BiCl3  is  soluble  in  a 
small  quantity  of  water,  more  water  separates  BiOCl, 
white,  insoluble  in  water,  soluble  in  acids.  HgCl2  and 
CuCL2  soluble  in  water,  CdCl2  deliquescent. 

Carbonates. — Neutral  salts  insoluble  in  water,  solu- 
ble in  acids.  Ag2CO3  and  CuCO3  are  readily  soluble  in 
H4NOH  +  Aq,  PbCO3  soluble  in  NaOH  -f  Aq.  From 
solutions  containing  members  of  the  group  Na2CO3-f  Aq 
precipitates  carbonates,  generally  basic,  insoluble  in  an 
excess  ;  (H4N).2CO3  +  Aq  precipitates  Hg  and  Hg2  as  in- 
soluble amine  compounds,  the  rest  as  carbonates  or  basic 
salts,  the  Ag  and  Cu  salts  being  readily  soluble  in  an 
excess. 

Sulphates. — CuSO4  and  CdSO4  readily  soluble; 
HgSO4  and  Bi,(SO4)3  decomposed  by  water,  giving  insolu- 
ble Hg.SO,;  yellow,  and  Bi.2H4SO8  white  ;  Ag.jSO4  sparingly 
soluble  ;  PbSO4  insoluble  in  water,  much  more  soluble  in 
strong  acids,  readily  soluble  in  NaOH+Aq,  or  in  solu- 
tions of  some  H4N  salts,  especially  H4NC2H3O2  and 
(H4N).C4H406. 


12  LECTURE  NOTES   ON 

Phosphates. — The  salts  of  the  forms  M"2H2(PO4)$ 
and  M"3(PO4)2  are  insoluble  in  water,  soluble  in  HNO3, 
many  of  them  in  H4NCl-J-Aq.  Ag3PO4  and  the  Cu  salts 
are  soluble  in  H4NOH  + Aq,  the  Pb  salts  in  NaOH-f  Aq. 
From  solutions  of  the  members  of  the  group  NaaHPO4 
-|-Aq  precipitates  Ag  as  Ag3PO4,  and,  if  added  in  excess, 
the  rest  in  the  form  M"8(PO4)j. 

Oxalates. — Insoluble  in  water,  soluble  in  HNOS. 
Ag2C8O4  and  CuC8O4  soluble  in  H4NOH  +  Aq;  PbC2O4 
soluble  in  NaOH  +  Aq. 

Chromates. — Ag2CrO4,  brick  red,  insoluble  in  water, 
soluble  iaH4NOH  -f  Aq,  or  HNO3;  Hg2CrO4,  red,  and 
Bi2(CrO4)3,  yellow,  insoluble  in  water,  soluble  in  HNO3 ; 
PbCrO4  bright  yellow,  insoluble  in  water  or  HC2H3O2, 
soluble  in  NaOH  +  Aq,  with  difficulty  in  HNO3. 
CuCrO4,  brown,  soluble,  and  HgCrO4  sparingly  soluble 
in  water. 

Tartrates. — The  Cu,  Cd  and  Hgs  salts  sparingly  solu- 
ble in  water,  the  rest  insoluble.  CuC4H4O6  is  readily  sol- 
uble inNaOH+Aq;  PbC4H4O6  soluble  in  H,C4H4O6+ 
Aq  or  in  NaOH  +  Aq. 

Cyanides. — Hg(CN),  soluble  in  water,  the  rest  insol- 
uble in  water,  soluble  in  HNO3,  except  AgCN.  In  KCN 
-f  Aq  AgCN,  Cu(CN),,  Cd(CN)2  are  soluble,  Pb(CN), 
and  Bi(CN)3  insoluble.  KCN  +  Aq  added  to  solutions 
of  Hg2  salts  precipitates  Hg,  forming  Hg(CN)2  in  so- 
lution. 

Ferrocyanides.— Pb,Fe(CN)6  and  CdsFe(CN)6  in- 
soluble in  water,  soluble  in  HNO3 ;  Ag4Fe(CN)6,  white, 
Cu,Fe(CN)6,  red  brown,  Bi4(Fe(CN)6)3,  white,  insoluble  in 
acids,  or  H4NOH  +  Aq. 


QUALITATIVE  ANALYSIS.  13 

GROUP  VI,    As,  Sb,  Sn. 

Metals. — As  and  Sb  brittle,  Sn  soft  and  malleable.  As 
volatilizes  without  fusion  ;  Sb  and  Sn  fuse  readily.  As  oxi- 
dizes at  ordinary  temperatures,  all  oxidize  readily  when 
heated.  As  and  Sb  are  hardly  attacked  by  HCl+Aq,  Sn 
is  easily  dissolved.  HNO3  oxidizes  all  three,  Sn  and  Sb 
without  solution.  HCl  +  Aq  with  HNO3  dissolve  all. 

Oxides. — As2O3  sparingly  soluble,  Sb2O3  and  Sb2O5 
slightly  soluble  -  in  water ;  the  rest  insoluble  in  water. 
All  soluble  in  HCl  +  Aq  or  HCl  +  Aq  with  HNO3.  As2O3 
readily  soluble  in  NaOH  +  Aq.  SnO2  is  often  insoluble 
in  HCl+Aq,  but  rendered  soluble  by  fusion  with  NaOH. 
SnO  and  Sb2O3  heated  in  air  give  SnO2  and  Sb2O4. 
As2O5  and  Sb2O5  when  heated  become  As2O3  and  Sb2O4. 

Hydrates. — H3  AsO3  known  only  in  solution  or  in 
its  salts,  H3AsO4  soluble.  HSbO3  slightly  soluble  in 
water.  The  other  hydrates  are  insoluble  in  water,  solu- 
ble in  HC1  +  Aq  or  NaOH  +  Aq.  The  SnIV  hydrates 
more  readily  soluble  in  KOH  +  Aq  than  in  NaOH  +  Aq ; 
one  modification  of  it  insoluble  in  acids,  and  with  great 
difficulty  soluble  in  KOH  +  Aq. 

Sulphides. — Insoluble  in  water  or  dilute  acids, 
readily  soluble  in  solutions  of  the  hydrates  or  sulphides 
of  Gr.  I.  If  dissolved  in  soluble  sulphides  they  form  sul- 
phur salts,1  or  if  in  solutions  of  the  hydrates,  a  mixture 
of  sulphur  salt  with  oxygen  salt.2  On  adding  acid  to 
either  of  the  solutions  the  original  sulphide  is  reprecipi- 

1  As2S3  +  (3(H,N)2S  +  Aq)  =  (2(H4N)3AsS3  +  Aq). 

2  AsaS3  +  (6NaOH  +  Aq)  = 

(Na3AsO3  +  NasAsS.  +  3H2O-f-  Aq). 


14  LECTURE  NOTES   ON 

tated.1  SnS  dissolved  in  yellow  (H4N)8S  +  Aq  precipi- 
tated as  SnSa.  As2S3,  yellow,  insoluble  in  strong 
HCl  +  Aq,  soluble  in  (H4N)SCO,  +Aq;  Sb.2S3  and 
Sb.(S5,  orange,  SnS,  brown,  SuS^,  yellow,  are  soluble  in 
strong  HC1  +  Aq,  insoluble  in  (H4N)iCO3  +  Aq.  Asv 
in  acid  solution  is  slowly  reduced  by  H2S  and  precipitated 
as  As.jS3. 

Chlorides.— AsCl3,  SbCl5,  SnCl4  volatile  liquids; 
SbCl3,  SnCl2  solids.  All  decomposed  by  water ;  SnCls  and 
SnCl4  slowly  or  when  treated  with  a  large  amount. 
SbCl3  gives  at  once  SbOCl  insoluble  in  water,  soluble  in 
acids ;  AsCl3  gives  As2O3  as  the  chief  product. 

Hydrides.— AsH8  and  SbH3,  gaseous,  are  formed 
when  a  soluble  As  or  Sb  compound  is  treated  with  Zn 
and  dilute  H2SO4.  .They  are  decomposed  below  red  heat 
into  Sb  or  As  and  H2.  Passed  into  AgNO3  -f  Aq, 
AsH3  precipitates  Ag  and  leaves  H3AsO3  in  solution ; a 
SbH3  precipitates  SbAg3.3 

Tartrates.— (SbO)KC4H4O6  soluble  in  water.  The 
presence  of  H2C4H4O6  in  sufficient  quantity  prevents  the 
precipitation  of  basic  Sb  salts  by  water. 

1  (2(H4N)3AsS3  +  6HC1  +  Aq)  = 

As2S3  +  3H2S  +  (6H4NC1  +  Aq). 
(Na3AsOs  -f  Na3AsS3  +  6HC1  +  Aq)  = 

As2S3  +  (6NaCl  +  aH2O  +  Aq). 
*  AsH,    +    (6AgN03    -+    3HaO  4-  Aq)  = 

3Ag2  +  (6HN03  +  H3AsO3  +  Aq). 
8  SbH3  +  (3AgN03  +  Ag)  =  SbAg,  +  (3HNO3  +  Aq). 


QUALITATIVE  ANALYSIS.  1  5 

ACIDS. 

GROUP  I. 

Ba  Salts  insoluble  in  water. 
i.  Acids  decomposed  in  acid  solution  by  H2S. 
M2CrO4          H3AsO4          M2SO3 


M3AsO3  M2S2O3 

2.  Acids  not  decomposed  in  acid  solution  by  H2S. 

a.  Ba  Salts  soluble  in  HC1  -f  Aq. 

H3PO4         HF         H2C4H4O6 
H3BO3  M2CO3 

H2C204  H4Si04    . 

b.  Ba  Salts  insoluble  in  HC1  +  Aq. 

H2SO4        H,SiF, 

GROUP  H. 

Ba  Salts  soluble,  Ag  Salts  insoluble  in  water. 

HC1  H4Fe(CN)6  HNO* 

HBr  H6Fe2(CN)12  HCIO 

HI  H2S  HCIO, 
HCN 


GROUP  III. 

Ba  and  Ag  Salts  soluble  in  water. 
HNO3  HC1O3  HC2H3OS 

ECHO* 


I 6  LECTURE  NOTES   ON 


PROPERTIES  OF  ACIDS. 

GROUP  I  1.  M2CrO<,  M3AsO>,  ILAsO*,  M.SOs,  M.S.Os. 

Chromates. — Salts  generally  insoluble  in  water,  the 
most  important  soluble  salts  being  those  of  Gr.  I.,  Sr,  Ca, 
Mg,  and  the  normal  salts  of  Mn  and  Zn.  The  acid  is 
unknown,  since  it  breaks  upon  liberation  from  its  salts  in- 
to H2O  and  CrO3 ;  it  also  gives  no  salts  of  the  form 
MHCrO4.  If  acid  be  added  to  a  solution  of  M2CrO4  it 
turns  from  yellow  to  red  with  the  formation  of  a  salt  of 
the  form  MjCrjO,,1  further  addition  of  acid  sets  CrO3 
free.8  If  HjSO4  is  used  the  CrO3  separates  as  a  red 
mass,  or  in  red  needles.  CrO3  heated  with  H2SO4  loses 
oxygen  and  becomes  Cr2(SO4)3, 3  with  HCl  +  Aq  it  gives 
Cr2Cl6  water  and  C19.4  Organic  matter  or  reducing 
agents,  like  H^  or  SO.^  effect  a  similar  change,  2CrO3 
becoming  Cr.2O3.6  In  any  case  the  change  of  CrO3  to 
Cr2O3  is  accompanied  by  a  corresponding  change  of  color 
from  red  to  green.  BaCrO4  and  PbCrO4,  yellow,  insolu- 
ble in  water  or  in  HC2H3O2.  Ag2CrO4,  brick  red,  soluble 
in  HNO3  or  H4NOH-f  Aq, 

Arsenites.— The  salts  of  Gr.  I.  are  soluble,  the  neu- 
tral salts  of  the  other  groups  insoluble  in  water,  though 
many  are  soluble  in  H4NC1  + Aq.  The  acid  is  unknown, 

1  (2K2CrO4  4-  H2SO4  +  Aq)  = 

(K2Cr2O7  +  KaSO4  +  H2O  +  Aq). 

5  (K2Cr2O7  +  H2SO4  +  Aq)  =  (2CrO3  +  K2SO4  +  H2O  +  Aq). 
8  4CrOs  +  6H2S04  -  2Cr2(SO4)3  +  6H2O  +  3O2. 
4  (2CrO3  +  I2HCI  +  Aq)  =  (Cr2Cl3  +  6H2O  -t-  Aq,+  3Cla. 
*  (2CrO3  +  6HC1  +  3H2S  4-  Aq)  = 

(CraCl8  +  6H2O   +  Aq)  +  38. 


QUALITATIVE  ANALYSIS.  I/ 

although  acid  salts  of  the  forms  MH2AsO3  and  M2H  AsO3 
are  known.  From  acid  solutions  of  all  salts  H2S  readily 
precipitates  As2S3  yellow.  Oxidizing  agents  convert  the 
salts  into  arseniates.  Cu2H2(AsO3)2  is  green,  insoluble  in 
water,  soluble  in  acids,  and  soluble  in  NaOH  +  Aq. 
On  warming  the  NaOH  solution  Cu2O2H2,  orange  yellow, 
is  precipitated,  Na3AsO4  being  left  in  solution.  Mg3(AsO3)2 
and  Ba3(AsO3)2  insoluble  in  water,  soluble  in  acids,  or 
H4NC1  -f  Aq  ;  Ag3AsO3,  pale  yellow,  insoluble  in  water, 
soluble  in  H4NOH  +  Aq  or  HNO3. 

Arseniates. — The  salts  resemble  the  phosphates 
closely.  Of  the  neutral  salts  only  those  of  Gr.  I.  are 
soluble.  The  acid  is  solid,  soluble  in  water.  From  acid 
solutions  of  its  salts  H2S  at  first  precipitates  nothing,  but 
on  long  standing,  or  more  quickly  on  warming,  it  is  re- 
duced and  As.,S3  is  precipitated.  SO2  reduces  it  quite 
rapidly  to  arsenious  acid  with  formation  of  H2SO4 ;  H2S 
then  at  once,  precipitates  As2S3.  Ba3(AsO4)2  and 
Mg3(AsO4).2  are  insoluble  in  water,  soluble  in  acids. 
Ag3AsO4,  red  brown,  insoluble  in  water,  soluble  in 
H4NOH  4-  Aq  or  HNO3.  Mg2(H4N)2(AsO4),,  insoluble 
in  water  or  H4NC1  +  Aq,  soluble  in  acid,  is  formed  when 
H4NOH  +  Aq,  H4NC1  +  Aq  and  MgSO4  +  Aq  are 
added  to  aqueous  solutions  of  arseniates.  A  solution  of 
(H4N)2MO4  in  HNO3  gives  no  precipitate  in  acid  solu- 
tions of  arseniates  in  the  cold,  but  gives  a  yellow  precipi- 
tate on  boiling. 

Sulphites. — The  neutral  salts  are  all  insoluble  or 
sparingly  soluble  in  water;  of  the  acid  salts  many  are 
soluble,  though  many  are  decomposed  by  boiling  their 
solutions,  neutral  salts  being  formed.  The  acid  is  un- 


1  8  LECTURE   NOTES   ON 

known.  From  its  salts  stronger  acids  liberate  SO2' 
soluble  in  water;  in  this  solution  H2S  forms  H.,S5O,;  with 
separation  of  S.  SO2  is  a  powerful  reducing  agent  but  is 
itself  reduced  by  nascent  H  with  formation  of  H2S.2 
BaSO3  is  insoluble  in  water,  soluble  in  HC1  -f  Aq  ;  from 
this  solution  C18  or  Br2  precipitate  BaSO4. 

Hyposulphites.  —  Most  of  the  salts  are  soluble  in 
water.  The  acid  is  unknown.  Stronger  acids  liberate 
from  its  salts  SO2  and  S.  The  same  decomposition3 
takes  place  when  HCl-fAq  is  added  to  solutions  of  its 
salts,  though  slowly  in  dilute  solutions.  With  H2S  in  acid 
solutions,  or  with  nascent  hydrogen  the  reactions  are  the 
same  as  with  the  sulphites.  BaS,O3  insoluble  in  water 
soluble  in  HCl-fAq.  Ag^Os,  white,  insoluble  in  water, 
soluble  in  solutions  of  hyposulphites  ;  blackens  on  heat- 
ing, Ag2S  being  formed.  PbS2O3,  insoluble  in  water,  solu- 
ble in  solutions  of  hyposulphites,  forms  PbS  on  heating." 

GROUP  I    2.  (a)  H3P04,  HnBO,,   H,C204,  HF,  M,C03, 

H.SiO*,  H.C  JLOn  ;  (b)  H2SO«. 

Phosphates.  —  Salts  of  the  forms  M3PO4  and 
M2HPO4  insoluble  except  those  of  Gr.  I.,  salts  of  the  form 
MH2PO4  soluble.  All  the  insoluble  salts  are  soluble  in 
acids,  and  these  solutions  are  precipitated  by  H4NOH 
+Aq;  the  precipitate  is  usually  a  phosphate  of  the  form 
M3PO4.  Ba3(PO4)2  and  Ca3(PO4)2,  insoluble  in  water,  are 
soluble  in  HCl  +  Aq  and  in  HC.2H3O2.  Ag,PO4,  pale 
yellow,  insoluble  in  water,  is  soluble  in  H4NOH-f  Aq  or 


1  (Na«SO3  +  2 

3  SOa  +  3H2  =  H3S  +  2H2O. 

3  (Na2S2O3  +  2HC1  +  Aq)  —  (2NaCl  +  H2O  +  SOa  +  Aq)  +  S. 

4  rbSa03  +  HaO  = 


QUALITATIVE  ANALYSIS.  19 

HNO3.  From  aqueous  solutions  of  the  phosphates 
MgSO4  +  Aq,  after  adding  H4NC1  -f  Aq  and  H4NOH  -f  Aq, 
precipitates  Mg.2(H4N)2(PO4).2  insoluble  in  water  or 
H4NCl-fAq,  soluble  in  acids.  In  acid  solutions  of  the 
phosphates  (H4N)2MO4  dissolved  in  HNO3  gives  a  yellow 
precipitate  in  the  cold,  insoluble  in  water  or  in  dilute 
acids,  if  (H4N).2MO4  be  in  excess,  readily  soluble  in 
excess  of  phosphate. 

Borates. — Only  the  salts  of  Gr.  I.  are  readily  soluble  in 
water,  though  many  salts  insoluble  in  water  are  soluble 
in  H4NC1  +  Aq.  The  acid  is  separated  from  its  salts 
by  stronger  acids  ;  soluble  in  water,  the  solution  turning 
turmeric  paper  red,  best  seen  when  the  paper  is  dried  at 
1 00°.  This  red  color  is  changed  to  greenish  black  when 
moistened  with  Na2CO3  -f-  Aq.  H3BO3  partially  volatil- 
ized by  evaporation  of  its  solution.  Its  alcoholic  solu- 
tion burns  with  a  green  flame..  The  Ba  and  Ca  salts  are 
insoluble  in  water,  soluble  in  HC1  +  Aq,  HC2H3O2  or 
H4NC1  -f  Aq.  The  Mg  salt  readily  soluble  in  H4NC1 
+  Aq. 

Oxalates. — Almost  all  the  neutral  salts,  except  those 
of  Gr.  I.  are  insoluble  in  water,  soluble  in  acids.  H4NOH 
precipitates  the  acid  solutions  of  many  of  the  salts  insolu- 
ble in  water,  those  of  Ba,  Sr  and  Ca  completely.  All  the 
salts  are  decomposed  by  ignition  ;  the  residue  consists  of 
carbonate,  oxide  or  metal.  The  acid,  readily  soluble  in 
water,  is  decomposed  when  heated  by  itself  or  with 
strong  H,SO4  into  CO,,  CO  and  H.O.1  With  the  dry  salts 
H2SO4  gives  the  same  reaction,  first  setting  the  acid  free, 
then  decomposing  it.  The  acid  or  its  salts  warmed  with 

]  HaCa04  =  H30  +  CO,  -f  CO. 


20  LECTURE    NOTES   ON 

dilute  H2SO4  and  MnO,  give  off  CO.,,  MnSO4  and  water 
being  formed.1  BaC,,O4  is  insoluble  in  water,  soluble  in 
HC1  4-  Aq.  CaCsO4  is  insoluble  in  water  or  HC,H:fO2, 
soluble  in  HCi  -\-  Aq.  AgaCsO4  insoluble  in  water, 
soluble  in  H4NOH  4  Aq  or  HNO3,  is  decomposed  with 
explosion  on  ignition,  Ag  being  left.  The  salts  of  Gr.  II. 
are  decomposed  on  boiling  with  a  concentrated  solution 
of  Na2CO3  with  formation  of  the  corresponding  carbonates 
and  Na2C2O4  in  solution. 

Fluorides. — Salts  of  Gr.  I.  readily  soluble,  as  also 
A12F6,  Cr2F6,  FesF6,  AgF,  HgF9.  The  rest  are  sparingly 
soluble  or  insoluble  in  water.  HF  is  liberated  from  its 
salts  by  strong  H2SO4  as  a  gas  readily  soluble  in  water, 
the  solution  characterized  by  its  power  of  dissolving 
SiO4  or  its  compounds  (glass).  A  fluoride  mixed  with 
silicates  or  SiO... gives,  on  heating  with  strong  HSSO4,  SiF4 
fuming  in  the  air,  and  giving  with  water  H4SiO4,  gelatin- 
ous.2 Fluorides  not  decomposed  by  H.^SO.,  must  be 
fused  with  mixed  Na2CO3  and  K2CO3.  BaF8  and  CaF2, 
as  precipitated,  are  gelatinous  and  transparent,  soluble 
in  hot  HCI  4-  Aq,  though  with  difficulty,  soluble  in 
H4NC1  4  Aq. 

Tartrates. — The  neutral  salts  of  Grs.  I.  and  III.  as 
well  as  of  Fe2  and  Co  readily  soluble  in  water.  The 
acid  is  very  soluble  in  water,  and  its  presence  prevents 
partially  or  wholly  precipitation  with  NaOH  4  Aq, 
H4NOH  4  Aq,  Na,CO,  4Aq,  or  (H4N)8CO8  4-  Aq.  The 
acid  and  its  salts  char  on  heating,  giving  off  an  odor  like 

1  (H2C2O4  +  HaSO4  +  Aq)  +  MnOa  = 

(MnSO4  +  2H2O  +  Aq)  +  2CO2.    • 
8  (3SiF4  +  4H2O  +Aq)  =  H.SiO,  +  (2H2SiF6  +  Aq). 


QUALITATIVE  ANALYSIS.  21 

burnt  sugar.  BaC4H4O6  insoluble  in  water,  soluble  in 
HC1  +  Aq  or  H4NC1  +  Aq.  CaC4H4O6  insoluble  in 
water,  soluble  in  HC1  or  HC2H3O2,  quite  soluble  in 
H4NC1  +  Aq,  readily  soluble  in  cold  NaOH  +  Aq,  re- 
precipitated  gelatinous  on  boiling ;  Ag;>C4H4O6,  white,  in- 
soluble in  water,  soluble  in  H4NOH  +  Aq  or  HNO3 ; 
blackens  immediately  on  boiling  from  separated  Ag. 
KHC4H4O6  is  sparingly  soluble  in  cold  water,  HC2H3O2 
or  H2C4H4O6+ Aq  readily  soluble  in  mineral  acids  or  solu- 
tions of  hydrates  of  Gr.  I. 

Carbonates. — The  neutral  salts  are  all  insoluble  in 
water,  except  those  of  Gr.  I.  ;  the  acid  salts  are  generally 
soluble,  though,  if  their  solutions  are  boiled,  all  but  those 
of  Gr.  I.  are  decomposed,  and  neutral  salts  precipitated. 
The  acid  is  unknown,  since  it  breaks  up  upon  liberation 
from  its  salts  into  water  and  CO2,  a  gas  heavier  than  air, 
quite  soluble  in  water.  CO2  gives  with  CaO2H2  CaCO3, 
white.  BaCO3  insoluble  in  water,  soluble  in  acids. 
Ag2CO3,  white,  insoluble  in  water,  soluble  in  H4NOH 
+  Aq  or  HNO3. 

Silicates. — The  silicates  of  Gr.  I.  are  alone  soluble  in 
water  ;  many  of  the  insoluble  salts  are  decomposed  by 
strong  acids  with  the  separation  of  H4SiO4.  When  the 
'acid  is  liberated  from  its  salts  by  acids,  the  greater  part 
generally  separates  in  a  gelatinous  form,  though  more  or 
less  remains  in  solution.  If  such  an  acid  solution  is 
evaporated  to  dry  ness,  all  its  Si  is  left  as  a  hydrate,  insol- 
uble in  water  or  acids  (except  HF1  +  Aq).  H4SiO4  when 
once  formed  is  insoluble  in  water  or  acids  (except  HF 
+Aq),  though  soluble  in  NaOH+Aq,  and  reprecipitated 
from  this  solution  by  H4NC1  +  Aq.  It  loses  water  readily, 


22  LECTURE   NOTES   ON 

and  on  ignition  SiO2  is  left  insoluble  in  a  bead  of  microcos- 
mic  salt  (NaH4NHPO4).  All  silicates  are  decomposed 
by  fusion  with  mixed  Na2CO3,  and  K2CO3.  The  Ba,  Ca 
and  Ag  salts  are  insoluble,  decomposed  by  HC1  +  Aq. 

Sulphates. — The  normal  salts  are  all  soluble,  except 
BaSO4,  SrSO4  and  PbSO4,  insoluble,  and  CaSO4  sparing- 
ly soluble.  The  acid  has  great  affinity  for  water,  and 
dissolves  with  evolution  of  heat.  When  strong  it  black- 
ens organic  water.  Sulphates,  when  heated  on  charcoal 
with  Na2CO3  in  the  inner  blowpipe  flame,  give  Na2S. 
BaSO4,  white,  insoluble  in  water  or  acids. 

GROUP  H    HC1,  HBr,  HI,  HCN,  H«Fea(CT)e, 

H.Fea(CT)n,  H.S. 

Chlorides. — All  soluble  except  AgCl,  Hg2Cl2  insolu- 
ble, and  PbCl2  sparingly  soluble  in  water.  From  its 
salts  H2SO4  liberates  HC1  (with  effervescence,  if  little  or 
no  water  is  present),  a  gas  very  soluble  in  water  ;  HSSO4 
and  MnO8  evolve  Clj,1  a  greenish  gas,  somewhat  soluble 
in  water,  which  bleaches.  AgCl  insoluble  in  water,  or 
HNO3,  soluble  in  H4NOH  +  Aq. 

Bromides. — Salts  soluble  except  AgBr  and  Hg2Br2. 
From  its  salts  H2SO4  liberates  HBr,  a  gas  very  soluble 
in  water,  but  mixed  with  more  or  less  Br2 ;  H2SO4  and 
MnO2  liberate  Br2,  a  red  volatile  liquid  soluble  in  water, 
its  vapors  red.  In  solutions  of  the  bromides  C12  -f-  Aq 
liberates  Br2,  which  colors  the  liquid  red.  The  Br2,  thus 
liberated,  can  all  be  collected  in  a  little  CS2,  in  which 
it  is  much  more  soluble  than  in  water.  An  excess  of 
C12  bleaches  the  color. 

1  2NaCl  +  3H.SO4  +  MnOa  = 

2NaHSO4  +  MnSO4+  2 


QUALITATIVE   ANALYSIS.  23 

Iodides. — Soluble  except  Agl,  yellowish  white,  Hg2Ia, 
greenish,  Hgl.2,  red,  PbI2,  yellow,  and  Bijg,  insoluble  in 
water.  From  its  salts  H^SC^  liberates  HI,  but  it  is  at 
once  oxidized  and  I2  set  free.  I2  is  almost  insoluble  in 
water,  readily  soluble  in  CS.,,  which  it  colors  violet ;  solu- 
ble, also,  in  solutions  of  iodides  with  a  deep  brown  color. 
It  sublimes  with  gentle  heat,  its  vapor  being  violet.  C13 
liberates  I2  from  its  salts,  an  excess  of  C12  then  converts  it 
into  colorless  IC18.  I2  gives  with  dilute  starch  paste  in  a 
slightly  acid  solution  a  deep  blue  compound  of  starch  and  I, 
bleached  by  heat  or  C12.  Agl  insoluble  in  water  or  HNO3, 
scarcely  soluble  in  H4NOH  +  Aq,  soluble  in  solutions  of 
iodides. 

Cyanides.— Salts  of  Grs.I.  and  II.  and  Hg(CN)2  solu- 
ble, the  rest  insoluble  in  water  though  many  are  soluble 
in  solutions  of  cyanides.  HCN  is  a  volatile  liquid  soluble 
in  water.  From  the  soluble  salts  even  dilute  acids  liber- 
ate the  acid ;  strong  H2SO4  decomposes  it,  giving  CO. 
The  insoluble  salts  are  all  decomposed  by  ignition. 
Many  of  the  insoluble  salts  are  decomposed  by  HC1 
+  Aq,  all  by  strong  H,SO4.  AgCN,  white,  insoluble  in 
water  or  dilute  HNO3,  soluble  in  H4NOH  +  Aq,  or  in 
solutions  of  cyanides  of  Grs.  I.  and  II. 

Ferrocyanides.— All  insoluble  in  water  except  the 
salts  of  Grs.  I.  and  II.  Many  of  the  salts  are  colored, 
and  all  the  insoluble  salts  decomposed  by  NaOH  +  Aq 
or  H,SO4.  H4Fe(CN)6  is  a  white  solid  readily  soluble 
in  water.  C12  converts  K4Fe(CN)6  in  solution  into 
K6Fe2(CN)la.  Ag4  Fe(CN)6,  white,  insoluble  in  water, 
H4NOH+  Aq  or  HNO3.  (Fe2)2  (Fe(CN)6)3,  blue,  and 
Cu2Fe(CN)6,  red  brown,  insoluble  in  water,  or  HC1  +  Aq. 


24  LECTURE  NOTES   ON 

Ferricyanides.— Salts  of  Grs.  I.  and  II.  and  Fe2  solu- 
ble in  water.  Many  of  the  salts  are  colored,  and  all  insolu- 
ble salts  decomposed  by  NaOH  +  Aq  or  H5SO4.  The 
acid,  H6Fe2(CN)12,  is  readily  soluble  in  water  and  convert- 
ed by  reducing  agents  into  H4Fe(CN)6.  Ag6Fe.,(CN),2,  or- 
ange, insoluble  in  water,  or  HNO3,  soluble  in  H4NOH 
+  Aq.  Fe3Fes(CN),j  blue,  insoluble  in  water,  or  HCl 
+  Aq.  FesFe^CN)^  soluble  in  water,  the  solution  brown. 

Sulphides.— The  salts  of  Grs.  I.  and  II.  soluble,  the  rest 
insoluble  in  water.  The  salts  of  Gr.  VI.  soluble  in  NaOH 
4-  Aq.  Most  salts  attacked  by  hot  HCl  +  Aq,  and  all  by 
HCl  +  Aq  with  HNO3.  Solution  is  effected  by  HCl 
+Aq  with  liberation  of  the  acid  H8S,  a  gas  somewhat  sol- 
uble in  water  ;  by  HNO3,  or  HCl  +  Aq  with  HNO;{,  with 
separation  of  S,  which  by  boiling  is  slowly  oxidized  to 
H2SO4.  AgsS,  black,  insoluble  in  H4NOH  +  Aq,  solu- 
ble in  hot  HNO3. 

GROUP  m.    HN03,  HClOa,  HCa  HaO*. 

Nitrates. — Normal  salts  all  soluble  in  water.  From 
its  salts  H2SO4  liberates  HNO3,  a  fuming  liquid,  perfectly 
soluble  in  water.  By  the  action  of  HNO3  upon  Cu,  NO 
is  formed !,  a  colorless  gas,  which  with  the  O  of  the  air 
forms  NOj,  orange  red.  NO  is  also  soluble  in  a  concen- 
trated solution  of  FeSO4,  forming  a  solution  colored 
black,  brown,  or  reddish,  according  to  its  concentration. 
On  heating  the  solution  NO  is  set  free.  All  the  salts 
deflagrate  when  heated  on  charcoal,  and  all  are  decom- 
posed by  ignition. 

Chlorates. — Normal  salts  all  soluble  in  water.    H2SO4 

1  3Cu  +  (8HNO3  +  Aq)  = 

(3Cu(NO,)a  +   4H20  +  Aq)  +  2NO. 


QUALITATIVE   ANALYSIS.  2$ 

added  to  the  chlorates  liberates  C1.,O4,  a  yellow  green  gas, 
smelling  like  C12  and  bleaching,  the  H^SOj  becoming  yel- 
low. Heat  must  be  avoided  or  the  decomposition  is  ac- 
companied by  explosion.  HC1  -f-  Aq  liberates  a  gas  of 
similar  color  and  odor,  C16O13.  HC1O3  is  liquid,  easily  de- 
composed, and  readily  soluble  in  water.  All'  the  salts 
deflagrate  when  heated  on  charcoal,  and  are  decomposed 
on  ignition  into  chloride  and  O2. 

Acetates. — The  normal  salts  are  all  soluble  in  water, 
although  many  are  decomposed  by  boiling  their  solutions 
into  insoluble  basic  salts.  The  salts  are  all  decomposed 
by  ignition  ;  aceton,  C3H6O,  is  almost  always  one  of  the 
products  of  decomposition,  and  generally  HCaHaOjj. 
Salts  of  Grs.  I.  and  II.  give  a  residue  of  carbonate,  the 
rest  either  metal  or  oxide,  generally  mixed  with  C. 
Feo(CaHsOj)8  gives  a  deep  red  solution,  which  on  boiling 
deposits  all  the  Fe2  as  a  brown  basic  salt  insoluble  in  water. 


COURSE   OF   ANALYSIS. 

PRELIMINARY    EXAMINATION. 

The  physical  properties  of  the  substance  under  exam- 
ination must  first  be  carefully  noted.  A  solid  must,  if 
possible,  be  reduced  to  fine  powder ;  a  portion  of  a 
liquid  should  be  evaporated  to  dryness,  and  the  residue, 
if  any  is  left,  powdered.  A  small  quantity  only  is  needed 
for  each  test. 

Heat  in  a  Bulb  Tube. 

Water  is  given  ofE — Crystal   water  usually  given 
off  with   fusion,  water    of   constitution   without ;   water 
mechanically  enclosed  often  with  decrepitation.      If  the 
2 


26  LECTURE  NOTES  ON 

water  has  an  alkaline  reaction,  H4N  is  present ;  if  an 
acid  reaction,  some  volatile  acid  as  H2SO4,  HC1,  HNO,, 
etc. 

Gas  escapes. —  6>2  shows  presence  of  nitrates,  chlo- 
rates, or  dioxides  ;  a  glowing  match  kindles. 

CO}  shows  presence  of  carbonates,  or  certain  oxa- 
lates  ;  a  drop  of  CaOsH2  +  Aq  rendered  turbid. 

CO  shows  presence  of  H2C2O4  or  some  of  its  salts  ; 
burns  with  a  blue  flame. 

JFf^S  shows  presence  of  hydrous  sulphide  ;  recognized 
by  its  odor. 

CN  formed  from  cyanides  decomposed  by  heat; 
recognized  by  odor,  or  burning  with  crimson  flame. 

NO}  shows  presence  of  nitrates  ;  recognized  by  orange 
red  color,  and  odor. 

C/2,  Br*  or  /2  liberated  from  chlorides,  bromides  or 
iodides  which  are  decomposed  by  heat. 

H*N  usually  shows  the  decomposition  of  an  H4N 
salt ;  recognized  by  test  paper,  and  odor. 

SO*  often  formed  by  decomposition  of  sulphates. 

Sublimate  formed. 

6*  sublimes  from  many  sulphides  in  red  brown  drops  ; 
solidifies  yellow  on  cooling. 

72  from  many  iodine  compounds ;  vapor  violet,  the 
sublimate  black. 

H±N.     Most  salts  give  white  crystalline  sublimates. 

Hg  and  some  of  its  compounds.  Hg  white  metallic 
globules ;  HgS  black,  turns  red  when  rubbed  ;  HgCl2 
melts  and  sublimes  white,  Hg,Cl2  sublimes  without  melt- 
ing. HgI2,  red,  sublimes  yellow,  turns  red  when  rubbed. 

As  and  some  of  its  compounds.     As  gives  a  metallic 


QUALITATIVE  ANALYSIS.  2/ 

mirror,  As2O3   a   crystalline    sublimate  ;  As.;S3   sublimes 
reddish  yellow  when  hot,  yellow  when  cold. 

Sb^Os  melts  and  sublimes  in  needles. 

HjC^Oi  sublimes  in  part,  white  and  crystalline. 

Residue  left  -with  change  of  color. — A  black 
residue  may  be  due  to  the  formation  of  a  black  oxide,  or 
to  carbonization  showing  the  presence  of  an  organic  acid 
or  other  organic  matter.  In  the  latter  case  a  characteris- 
tic odor  is  usually  evolved.  If  the  residue  effervesces 
with  acids,  while  the  original  substance  did  not,  it  shows 
the  presence  of  acetates,  tartrates,  oroxalates  of  Grs.  I.  and 
II.  The  following  changes  of  color  are  common.  The 
residue 

Yellow      while  hot   White       when  cold     ZnO 
Red  brown     "     "     Yellow  "        "       PbO 

Red  brown     "     "     Pale  yellow  "        "       Bi.2O3 
Black  "     "     Red  "        "       Fe2O3 

Heat  on  charcoal  in  inner  blowpipe  flame. — 
Many  of  the  reactions  of  the  closed  tube  are  repeated.  If 
the  odor  of  SOS  is  perceived  sulphides  are  probably 
present.  A  garlic  odor  shows  presence  of  As. 

Deflagration. — Shows  presence  of  nitrates  or  chlo- 
rates. 

Substance  melts  and  runs  into  the  charcoal.  Salts 
of  Gr.  I. 

Residue  white ;  infusible,  but  luminous  when  heat- 
ed, Gr.  II.,  Zn,  A12  or  SiO2.  The  residue  must  then  be 
moistened  with  Co(NO3)2  +  Aq  and  again  heated  in  the 
outer  flame.  If  the  residue  becomes  colored,  blue  shows 
A12 ;  green  Zn ;  flesh  colored,  Mg ;  blue  green,  Sn. 
Phosphates  and  silicates  also  give  a  blue  color. 


28  LECTURE  NOTES   ON 

Residue  colored  or  metallic,  with  or  without  a  coat- 
ing upon  the  charcoal.  In  this  case  some  of  the  sub- 
stance must  be  mixed  with  Na2CO3  and  heated  in  the 
inner  blowpipe  flame  on  charcoal.  The  color  of  the 
coating  around  the  assay,  and  the  nature  of  the  metallic 
globule  must  be  noted.  If  no  one  large  globule  can  be 
obtained,  the  charcoal  under  the  assay  must  be  cut  out 
and  ground  up  with  water  in  a  mortar.  The  charcoal 
can  readily  be  washed  away  and  the  metal  left,  in  span- 
gles, if  malleable.  The  presence  of  As  shown  by  garlic 
odor.  The  character  of  the  metallic  globules  of  the  re- 
ducible metals  and  the  colors  of  the  coating  on  the  char- 
coal are  as  follows : 

ON    CHARCOAL   WITH    NaaCO3. 
GLOBULE.     •  COATING. 

Hot.  Cold. 

Bi  Brittle  Dark  orange  Lemon  yellow 

Sb  "  White  White 

Ag  Malleable  (Dark  red) 

Sn  "  Pale  yellow  White 

Pb  "  Orange  yellow  Yellow 

Cu  " 

Zn  Yellow  White 

Ccf  Red  brown  Red  brown 

As  White 

Reduced  but 
not  fused. 

Examination  with  Borax. 
A  small  quantity  of  the  substance  is  melted   into   a 


QUALITATIVE  ANALYSIS.  29 

borax  bead  upon  platinum  wire.  It  should  first  be 
heated  in  the  outer  blowpipe  flame,  afterwards  in  the 
inner  flame,  the  colors  of  the  bead,  both  hot  and  cold, 
being  carefully  noted.  An  excess  of  substance  must  be 
avoided.  The  colors  of  the  various  beads,  both  hot  and 
cold,  in  the  inner  and  outer  flames,  are  as  follows : 


BORAX    BEADS. 


OUTER   FLAME. 


INNER   FLAME. 


Hot. 

Cold. 

Hot. 

Cold. 

Cu 

Green 

Blue 

Colorless 

Red  opaque 

Co 

Blue 

Blue 

'Blue 

Blue 

Ni 

Violet 

Red  brown 

Gray 

Gray 

Fe 

Red 

Yellow 

Bottle  green 

Bottle  green 

Mn 

Violet 

Amethyst 

Colorless 

Colorless 

Cr 

Green 

Green 

Green 

Green 

Flame  Colorations. 

The  coloration  given  by  the  substance  to  the  flame  of 
the  lamp  often  gives  more  or  less  positive  indications. 
The  substance  is  introduced  into  the  edge  of  the  flame 
on  platinum  wire. 

Red  flames.  K,  violet ;  Li,  carmine  ;  Sr,  crimson  ; 
Ca,  orange  red. 

Yellow  flames.     Na. 

Green  flames.  Cu  (most  salts)  bright  green ;  Ba,  yel- 
low green  ;  H3BO3  pale  green. 

Blue  flames.     CuCl2,  bright  blue ;  Pb,  As  pale  blue. 

Examination  with  ILS04. 
On   heating    the     substance  with    strong  H2SO4    the 


30  LECTURE   NOTES   ON 


presence  or  absence  of  certain  acids  may  be  established. 
If,  on  adding  H-jsO,,  HC1O3  is  found  present,  heat  must 
not  be  applied? 

HNO3,  HCl,  HF,  H2S,  CO2  are  liberated  from  their 
compounds.  SO8  shows  presence  of  sulphites  or  hypo- 
sulphites ;  CO  of  oxalates  or  cyanides.  HC2H3O3  set 
free  and  recognized  by  odor.  Br2  and  I2  liberated  from 
bromides  and  iodides,  C12O4  from  chlorates.  Tartrates 
blacken. 

SOLUTION. 

Treatment  with  Water. 

The  substance  in  fine  powder  must  be  treated  with 
water,  first  cold  then  hot.  Most  salts  are  more  readily 
soluble  in  hot  water  than  in  cold  ;  in  a  few  cases  the  re- 
verse is  true,  and  some  salts,  though  soluble  in  cold 
water,  are  decomposed  by  boiling  water  into  insoluble 
basic  salts.  Salts  of  Bi,  and  some  salts  of  Sb,  Hg  and 
Hg2  are  thus  decomposed  even  by  cold  water. 

After  boiling  for  some  time,  if  a  portion  remains  undis- 
solved,  it  must  be  collected  upon  a  filter,  washed  and 
treated  with  acids.  If  there  be  any  doubt  whether  even 
a  part  of  the  substance  is  soluble,  a  few  drops  of  the  fil- 
trate must  be  evaporated  on  platinum  foil. 

The  reaction  of  the  aqueous  solution  should  be  tested, 
or,  if  the  substance  under  examination  is  liquid,  the  re- 
action of  the  original  solution. 

An  alkaline  reaction  shows  the  presence  of  Gr.  I.  or 
II.  An  acid  reaction  may  be  due  to  the  presence  of  a 
free  acid  or  acid  salt,  or  due  to  the  presence  of  a  neutral 


QUALITATIVE   ANALYSIS.  31 

salt  with  acid  reaction.  In  the  first  case  a  drop  of 
Na2CO3  -f-  Aq  gives  no  precipitate,  or  the  precipitate 
which  is  formed  redissolves ;  in  the  second  the  turbidity 
is  usually  permanent. 

Treatment  with  Acids. 

For  the  solution  of  a  substance  insoluble  in  water 
HC1  +  Aq,  HNO3  or  a  mixture  of  the  two  (aqua  regia) 
is  used.  A  solution  in  HC1  +  Aq  is  much  the  best  for 
subsequent  work. 

Many  substances  are  soluble  in  dilute  acids,  though  in- 
soluble in  strong,  many  soluble  only  in  strong,  and  again 
many,  that  are  not  attacked  by  dilute  acids,  are  decom- 
posed, though  not  dissolved,  by  stronger  acids,  so  that 
solution  can  only  be  effected  by  treatment  with  strong 
acids  and  subsequent  dilution.  The  substance  should 
therefore  be  boiled  successively  with  HC1  +  Aq,  HNO3 
and  HC1  +Aq  with  HNO3,  using  first  dilute,  then  strong, 
and  finally  adding  water  to  that  which  has  been  boiled 
with  strong  acid. 

Effervescence  may  show  CO2  present,  or  if  HC1  -f  Aq 
is  used  H.2S  or  SO2.  With  HC1  +  Aq  HCN  is  often 
set  free  from  insoluble  cyanides,  or  C12  is  evolved 
if  dioxides  or  chromates  are  present.  S  or  gelatinous 
H4SiO4  are  also  often  separated.  Unless  As  or  Sb 
may  be  present,  the  solution  should  be  freed  from  any 
great  excess  of  acid  by  evaporation.  It  is  much  better, 
in  any  case,  to  avoid  an  excess  from  the  first,  taking 
care  also  that  the  solution  be  properly  diluted  before 
beginning  the  analysis.  HCl  +  Aq  and  HNO3  together 
dissolve  by  converting  into  chlorides. 


32  LECTURE   NOTES   ON 

If  the  substance  is  a  metal  or  alloy,  as  will  appear  in 
the  preliminary  examination,  it  should  be  treated  at  once 
with  hot  HNO3 — ,  i  part  strong  acid  to  3  of  water. 
Sb  and  Sn  are  oxidized  to  SnOa  and  Sb.2O3  (Sb2O4)  insol- 
uble in  water,  or  dilute  HNO3,  the  other  metals  are 
found  in  solution.  As  many  nitrates  are  insoluble  in 
strong  HNO3,  though  readily  soluble  in  water,  care  must 
be  taken  not  to  mistake  the  crystalline  nitrates  for  oxides 
of  Sn  or  Sb.  The  insoluble  residue  may  contain  a  part 
of  any  As  present. 

Treatment  of  Substances  Insoluble  in  Water  or 
Acids. 

The  most  common  substances  insoluble  in  water  or 
acids  are  :  BaSO4,  SrSo4,  (CaSO4),  PbSO4 ;  the  Ag  salts  of 
acids  of  Or.  II.,  except  Ag.2S ;  ignited  A12O3,  Cr.2O3  or 
SnO2 ;  SiO2  and  many  silicates  ;  CaF2,  S-  and  C. 

S  is  recognized  in  the  preliminary  examination.  C  is 
present  if  the  substance  is  black,  and  part  of  it  burns 
before  the  blowpipe.  If  Pb  and  Ag  have  not  been  found 
in  the  preliminary  examination,  special  tests  must  be 
made  for  their  presence.  Ag  may  be  found,  if  present, 
by  warming  the  substance  with  KCN  4-  Aq,  which  dis- 
solves all  the  Ag  salts  insoluble  in  acids,  and  testing  the 
filtrate  with  (H4N).2S  +  Aq.  To  test  for  Pb,  warm  the 
substance  with  H4NCsHaO2  -f  Aq,  which  dissolves 
PbSO4,  and  add  to  the  filtered  solution  (H2N),S  +  Aq. 
If  Ag  or  Pb  are  present  they  must  be  removed  by  suc- 
cessive treatment  with  H4NC2H3O.2  +  Aq,  and  KCN 
+  Aq.  If  S  is  also  present,  it  must  be  volatilized  in  a 
porcelain  crucible  after  the  removal  of  Pb  and  Ag.  If 


QUALITATIVE   ANALYSIS.  33 

S  is  present,  cold  KCN  -f-  Aq  must  be  used  for  the  re- 
moval of  Ag. 

The  substance  free  from  Agj  Pb  and  S,  may  then  be 
mixed  with  2  parts  Na,CO3,  2  parts  K2CO3,  and  i  part 
KNO3,  and  heated  to  quiet  fusion  in  a  platinum  cru- 
cible. From  the  cooled  mass  water  then  dissolves  alka- 
line salts  of  the  acids  present,  and  the  bases  are  left  as 
carbonates,  soluble  in  HCl  +  Aq,  after  thorough  washing. 
A12  is  found  in  solution,  and  Cr2  as  chromate.  To  find 
the  acids  of  the  insoluble  Ag  salts,  NaOH  +  Aq,  dilute, 
will  decompose  the  ferro-  and  ferricyanide,  sodic  salts  of 
those  acids  going  into  solution  by  boiling  ;  AgCl,  AgBr, 
Agl  and  AgCN  are  reduced  by  Zn  and  dilute  H2SO4 ;  in 
the  solution  HC1,  HBr,  HI  and  HCN  may  be  found.  If 
the  members  of  Gr.  I.  must  be  looked  for  in  silicates,  fuse 
with  4  parts  of  BaO2H2. 

Some  substances  insoluble,  or  slowly,  soluble,  in  acids, 
may  be  decomposed  with  advantage  by  NaOH  +  Aq. 
The  insoluble  ferrocyanides  and  ferricyanides  are  de- 
composed by  hot  NaOH  +  Aq,  into  sodic  salts  of  the 
acids  and  insoluble  or  soluble  hydrates.  The  solution 
may  therefore  be  examined  for  Pb,  Zn  and  A12,  and,  after 
their  removal,  for  the  acids,  although  it  must  be  remem- 
bered that  H6Fe2(CN)12  in  the  alkaline  solution  is  readily 
converted  into  H4Fe(CN)6  by  H2S.  The  portion  insolu- 
ble in  NaOH  -j-  Aq  may  be  dissolved  in  acids  and  tested 
as  usual. 

The  three  portions  of  any  substance,  that  soluble  in 
water,  that  soluble  only  in  acids,  and  that  insoluble  in 
water  and  acids,  must  be  separately  examined.  The. 
larger  portion  should  first  be  analyzed,  inasmuch  as  a 


34  LECTURE  NOTES   ON 

knowledge  of  its  constitution  may  greatly  facilitate  the 
analysis  of  the  smaller  portions. 


DETECTION  OF  BASES. 

The  bases  may  be  divided  according  to  their  behavior 
with  reagents  into  six  groups,  and,  for  convenience  in 
analysis,  these  groups  are  separated  from  each  other  by 
general  reagents  before  proceeding  to  test  for  the  individ- 
ual members  of  each  group.1  In  an  acid  solution  H2S 
precipitates  only  members  of  Grs.  V.  and  VI.  The  pre- 
cipitation is  complete,  unless  the  solution  is  very  strongly 
acid,  in  which  case  more  or  less  Pb  and  Cd  remain  in  so- 
lution. The  sulphides  of  the  two  groups  are  separated 
by  an  alkaline  solution,  the  sulphides  of  Gr.  V.  being  in- 
soluble, those  of  Gr.  VI.  soluble,  but  precipitated  by  the 
addition  of  acid.  As  the  HC1  +  Aq,  best  used  to  acidify 
the  solution,  precipitates  AgCl,  Kg^C^  andPbClj  (partial- 
ly), it  is  more  convenient  to  separate  these  by  nitration,  and 
test  for  them  apart.  The  members  of  Grs.  III.  and  IV. 
are  not  precipitated  by  H2S  in  a  solution  acidified  with 
HC1  -f-  Aq,  but  are  precipitated  by  (H4N)tfS  +  Aq  in  an 
alkaline  solution — Gr.  III.  as  hydrates,  Gr.  IV.  as  sul- 
phides. Grs.  V.  and  VI.  are  also  precipitated  by 
(H4N)8S  +  Aq,  though  the  precipitate  of  Gr.  VI.  redis- 
solves  in  an  excess.  Grs.  V.  and  VI.  must  therefore  be 
removed  before  precipitating  Grs.  III.  and  IV.  It  is 
more  convenient  not  to  separate  Gr.  III.  as  a  whole  from 
Gr.  IV.,  but  to  test  the  general  precipitate  for  members 
of  both  groups.  The  members  of  Gr.  II.  are  not  precipita- 
ted by  H.2S  or  (H4N)2S  +  Aq,  and  are  distinguished  from  Gr. 
1  Compare  table  of  bases  on  page  i. 


QUALITATIVE  ANALYSIS.  35 

I.  by  the  insolubility  of  their  carbonates.  (H4N)2CO3  + Aq 
precipitates  Ba,  Sr  and  Ca  as  carbonates,  but  as  Mg  is  not 
precipitated  as  carbonate  in  presence  of  H4N  salts,  it  is 
more  convenient  to  make  a  special  test  for  its  presence, 
and  remove  it  after  the  H4N  salts  have  been  expelled  by 
ignition.  (H4N).2CO3-|-Aq  precipitates  most  of  the  mem- 
bers of  Grs.  VI. -III.,  and  these  groups  must  therefore  be 
removed  before  the  precipitation  of  Gr.  II.  Members  of 
Gr.  I.  are  precipitated  by  no  general  reagent,  but  are  left 
in  solution  after  the  removal  of  the  higher  groups.  Since 
H4N  salts  are  used  as  reagents,  tests  for  H4N  must  be 
made  in  the  original  solution. 

GROUPS  V.  and  VI.   Ag,  Hg2,  Pb,  Hg,  Cu,  Bi,  Cu;  As,  Sb. 
Sn,  Sniv. 

To  the  solution  add  HC1  +  Aq.  If  a  white  precipitate  * 
falls,  it  may  contain  AgCl,  Hg2Cl2  and  PbCl2.  Filter, 
wash  the  precipitate  with  a  little  cold  water,  and  set  aside 
the  filtrate.  The  precipitate  must  then  be  washed  with  hot 
water ;  AgCl  and  Hg2CI2  are  insoluble,  PbCl2  is  dissolved, 
if  present,  and  by  adding  dilute  H2SO4  to  the  solution 
PbSO4  is  precipitated.  The  residue,  which  may  consist 
of  AgCl  and  Hg2Cl2,  is  next  treated  on  the  filter  with 
H4NOH  +  Aq.  Hg2Cl2,  if  present,  is  converted  into  black 
insoluble  [Hg,].2H4N2Cl2,  and  AgCl  is  dissolved.  To  the 

1  If  the  solution  is  alkaline,  on  the  addition  of  HC1  +  Aq  As2S3, 
Sb2S3  or  SnSj  may  be  precipitated ;  cyanides  dissolved  in  KCN 
+  Aq  may  be  thrown  down  ;  gelatinous  H  iSiO4  separated,  or  S  from 
alkaline  sulphides.  CO,,  II, S,  SO,  and  HCN  may  be  set  free 
AgCl  is  soluble  in  Hg(NO3)3  +  Aq,  but  is  precipitated  by  the  addi- 
tion of  HjNCaHaOj  +  Aq. 


36  LECTURE  NOTES   ON 

HjNOH  l  +  Aq  which  has  run  through  the  filter  is  then 
added  HNO3  in  excess  ;  if  Ag  is  present,  AgCl  is  precipi- 
tated, white  and  curdy,  or,  if  in  small  quantity,  opalescent. 
To  the  filtrate  from  the  precipitate  caused  by  HC1  4- Aq, 
add  H2S  +  Aq,  or  better,  pass  into  it  H2S ;  warm  for 
some  time,  adding  H2S  +  Aq  until  the  solution  smells 
strongly  of  it  after  shaking,  and  filter.  The  filtrate,  which 
may  contain  Grs.  I.— IV.  is  set  aside  ;  the  precipitate  may 
contain  PbS,  HgS,  CuS,  Bi,S3,  CdS,  As,S3,  Sb,S3,  SnS  and 
SnS.;.  It  must  be  washed  with  hot  water  until  AgNO3  gives 
no  precipitate  of  AgCl  in  the  wash  water,  and  then  gently 
warmed  with  very  little  yellow  (H4N).2S  +  Aq.  The  sul- 
phides of  Gr.  VI.  are  thus  dissolved:  Filter  and  set  the 
filtrate  aside  to  be  examined  for  members  of  Group  VI. 
The  precipitate,  which  may  contain  PbS,  HgS,  CuS,  BLS3 
and  CdS,  after  being  well  washed,  is  boiled  with  dilute 
HNO3.  HgS  alone  is  insoluble,  although  the  S  which 
separates  is  often  colored  with  a  little  of  one  of  the  other 
sulphides,  and  a  black  residue  must  therefore  be  tested 
for  Hg.  The  residue  is  filtered"  off,  dissolved  in  HC1 
-f  Aq  with  the  addition  of  a  very  little  KC1O3,  and  bright 
bits  of  Cu  wire  put  into  the  solution.  Hg,  if  present,  is 
deposited  on  the  Cu,  and  when  dried  may  be  sublimed  in 
a  bulb  tube.  The  HNO3  solution  filtered  from  HgS  or 
separated  S  may  contain  the  nitrates  of  Pb,  Cu,  Bi  and  Cd. 
If  Pb  has  already  been  found,  it  must  be  removed,  and 
if  not  found,  it  may  yet  be  present  in  quantity  too  small 
to  be  precipitated  by  HC1  +  Aq.  The  solution  must  be 

1  If  PbCL  is  not  completely  washed  out,  the  IL.NOH  +  Aq  is 
often  turbid  from  the  presence  of  a  basic  Pb  salt.  This  does  not 
interfere  with  the  detection  of  Ag,  as  it  dissolves  readily  in  HNO3. 


QUALITATIVE  ANALYSIS.  37 

concentrated  by  evaporation  until  the  greater  part  of  the 
HNO3  has  been  driven  off,  dilute  H2SO4  added,  the  solu- 
tion gently  warmed  and  allowed  to  stand  for  some  time. 
A  white  precipitate  is  PbSO4  and  shows  Pb  present.  If 
Pb  is  present,  the  solution  must  be  evaporated  with  dilute 
H2SO4  until  the  HNO3  is  all  expelled,  water  slightly  acid 
with  H2SO4  added,  and  the  insoluble  PbSO4  filtered  off. 
The  solution  now  may  contain  Cu,  Bi  and  Cd.  Add 
H4NOH  +  Aq  in  excess,  which  precipitates  BiO3H3  white 
and  flocculent,  if  Bi  is  present ;  if  the  solution  is  blue,  Cu 
is  present.  Filter  from  the  precipitated  BiO3H3.  If  the 
filtrate  is  not  blue,  a  very  small  quantity  of  Cu  may  be  de- 
tected by  acidifying  a  portion  with  HC2H3O2  and  adding 
K4Fe(CN)6  -f  Aq  which  precipitates  red  brown  Cu2Fe  (CN)6. 
If  Cu  is  absent,  (H4N)2S  +  Aq  added  will  precipitate 
yellow  CdS.  If  Cu  is  present,  precipitate  CuS  and 
CdS  with  H2S  +  Aq,  and  boil  the  mixed  sulphides  with 
dilute  H2SO4,  avoiding  exposure  to  the  air.  CdS,  if  pres- 
ent, is  alone  dissolved,  and,  after  filtering  off  the  undis- 
solved  CuS,  maybe  precipitated  by  H2S,  or  H4NOH  -f 
Aq  and  (H4N)2S  +  Aq,  as  yellow  CdS. 

The  (H4N)aS  +  Aq  solution  which  may  contain  Gr. 
VI.  is  acidified  with  dilute  HC1  +  Aq.  The  sulphides 
are  thus  precipitated  mixed  with  S.  If  too  much 
(H4N)2S  +  Aq  was  not  used  for  solution,  the  presence  of 
the  sulphides  is  readily  recognized.  The  precipitate, 
which  may  contain  As2S3,  Sb2S3  and  SnSa,1  is  collected  on 
a  filter  and  washed,  then  treated  in  the  cold  with 
(H4N).,CO3  +  Aq.  As.2S3  dissolves  and  may  be  precipi- 

1  Brown  SnS  dissolved  in  yellow  (H4N)2S  +  Aq  is  precipitated  by 
HC1  + Aq  as  yellow  SnS2. 


38  LECTURE  NOTES   ON 

tated  from  the  filtered  solution  by  acidifying  with 
HC1  +  Aq  as  yellow  As2S3,  if  As  is  present.  In  order 
to  confirm  the  presence  of  As,  the  precipitate  must  be 
thoroughly  dried,  "mixed  with  dry  KCN  and  Na2CO3,  and 
the  mixture  heated  in  <a  bulb  tube ;  As,  if  present,  is 
sublimed  as  a  metallic  mirror. 

The  residue  insoluble  in  (H4N)aCO3  +  Aq  may  con- 
tain Sb2S3  and  SnS2.  It  is  dissolved  in  strong  HC1  +  Aq, 
with  the  addition  of  a  little  KC1O3,  if  necessary ;  any 
large  excess  of  HC1  4-  Aq  must  be  avoided.  The  solu- 
tion is  diluted  and  into  it  are  put  bits  of  platinum  foil  and 
Zn  in  contact.  When  the  evolution  of  H2  has  ceased, 
Sb  and  Sn,  if  present,  are  found  deposited  upon  the  foil, 
Sb  black,  and  Sn  silver  white.  The  foil  must  be  care 
fully  washed  and  warmed  with  HC1  +  Aq.  Sn,  if  pres 
ent,  is  dissolved  as  SnCl2,  which  may  be  recognized  in 
solution  by  adding  HgCl2  -f-  Aq  ;  Hg2Cl2  being  precipi- 
tated, often  gray  from  Hg.1  Sb  may  be  recognized  by 
the  black  color  of  the  foil.  If  confirmation  is  needed, 
it  may  be  dissolved  in  H.2C4H4O6  +  Aq  with  the  addition 
of  a  few  drops  of  HNO3 ;  from  this  solution  H2S  pre- 
cipitates, after  addition  of  HC1  -f-  Aq,  orange,  Sb2S3 
if  Sb  is  present. 

Groups  III.  and  IV.— AL,  Cr,,  Fe*,  Fe,  Ni,  Co,  Mn,  Zn, 

and  phosphates  and  oxalates  soluble  in  acids  only. 

To  the  filtrate  from  the  general  precipitate  of  Grs.  V. 
and  VI.,  or  to  the  solution  found  not  to  contain  Grs.  V.  and 
VI.,  add  H4NC1  +  Aq  and  H4NOH  +  Aq  in  slight  ex- 
cess ;  heat  almost  to  boiling,   add  (H4N).,S  and   keep 
1  (SnCl2  +  -2HgCla  +   Aq)  =  Hg2Cla   +   (SnCl4  +  Aq). 
(SnCl2  +  HgCl2  +  Aq)  =  Hg+  (SnCl4  +  Aq). 


QUALITATIVE  ANALYSIS.  39 

warm  for  some  time.  The  precipitate  is  more  granular 
if  the  solution  is  shaken  well  in  a  corked  flask.  Filter  as 
rapidly  as  possible  and  wash  with  hot  water,  best  with  ad- 
dition of  a  little  (H4N)2S  +  Aq.  The  filtrate,  which  may 
contain  Grs.  I.  and  II.,1  must  be  concentrated  by  evapora- 
tion, filtered  if  necessary,  and  set  aside.  The  color  of  the 
precipitate  gives  some  indication  of  what  is  present.  It 
may  contain  A12O6H6,  Cr2O6Hfl,  FeS,  MnS,  ZnS,  NiS,  or 
CoS,  together  with  phosphates  or  oxalates  of  A12,  Cr2 
and  Gr.  II.,  and  must  be  tested  for  all,  if  it  is  black.  First 
treat  with  cold  dilute  HC1  +  Aq ;  NiS  and  CoS  alone  are 
insoluble,  the  rest  go  into  solution.  If  a  black  residue  re- 
mains Ni  or  Co,  or  both,  are  present.  The  residue  must 
be  collected  on  a  filter  and  tested  for  Co  with  borax.  A 
blue  bead  in  the  inner  and  outer  flames  shows  Co  is  pre- 
sent, and  Ni  may  be.  If  Co  is  absent  and  the  bead  gives 
the  Ni  reactions,  the  black  residue  was  NiS.  If  Co  is 
present,  dissolve  in  HC1  -f-  Aq  and  HNO3,  add  NaOH 
-f  Aq  in  excess  and  filter.  Dissolve  the  hydrates  thus 
obtained  in  as  little  as  possible  concentrated  KCN  -{-  Aq, 
add  NaOH  +  Aq  and  Br2  +  Aq.  On  boiling  Ni,  if  present, 
is  precipitated  as  Ni2O6H6,  Co  remains  in  solution  as 
Na6Co2(CN),2. 

The  solution  in  HC1  +  Aq,  filtered  from  NiS  or  CoS, 
if  a  residue  was  left,  is  boiled  until  H2S  is  all  expelled,  a 
little  HNO3  is  added,  the  solution  again  boiled  till  the 
greater  part  of  the  acid  is  driven  off  and  then  diluted  with 

1  If  Ni  is  present  more  or  less  NiS  is  dissolved  in  the  excess  of 
(H4N),S  +  Aq,  especially  if  much  H4NOH  -f  Aq  is  added;  the  fil- 
trate is  then  brown  or  black.  By  evaporating  and  acidifying  with 
IIC2H3O2  or  HC1  +  Aq,  NiS  is  precipitated. 


40  LECTURE  NOTES   ON 

water.  If  it  is  not  already  known  whether  H3PO4  and 
H2C2O4  are  present  or  not,  this  must  now  be  determined. 
If  H3PO4  and  H2C2O4  are  absent,  neutralize  the  little 
free  acid  in  the  solution  with  NajCOg,  care  being  taken 
that  no  permanent  precipitate  is  formed,  then  add  BaCO3 
in  the  cold  and  allow  the  whole  to  stand  for  some  time, 
stirring  occasionally.  The  precipitate  may  contain 
A12O6H6,  Cr2O6H6  or  Fe2O6H6  together  with  the  excess  of 
BaCO3,  the  nitrate  may  contain  Mn  or  Zn  with  BaCl2. 
Dissolve  the  precipitate  collected  on  a  filter  in  dilute 
HC1  +  Aq,  warm  gently  and  add  H4NOH  -f  Aq  which 
will  precipitate  as  hydrates  Fe2,  A12  and  Cr.:,  if  present. 
This  precipitate  must  be  collected  on  a  filter,  washed, 
dried  and  dissolved  in  a  little  strong  HNO3.  The  solu- 
tion is  then  boiled  with  a  few  crystals  of  KC1O3  for  sev- 
eral minutes,  and  NaOH  +  Aq  added  in  excess. 
Fe2O6H8  is  precipitated,  if  Fe  is  present,  and  the  solution 
may  contain  Al2O6Na6  and  Na.>CrO4.  In  a  part  of  the 
solution  A12  may  be  precipitated  by  adding  H4NC1  +  Aq 
as  A12O6IV  or,  after  acidifying  with  HNO3,  H4NOH 
+  Aq  causes  the  same  precipitate;  another  portion  of 
the  solution  is  acidified  with  HC8H8O8  and  BaCl2  +  Aq 
added,  which  precipitates  BaCrO4,  if  Cr2  is  present.  If 
NaOH  -f  Aq  precipitates  Fe2O6H6,  the  original  solution 
must  be  tested  by  adding  to  a  small  portion  K6Fe2(C]Sr),? 
-f  Aq,  which  gives  blue  Fe3Fe2  (CN),2,  if  Fe  is  present ; 

1  NaOH  often  contains  silicate,  and  gelatinous  H4SiO4  is  then 
precipitated  here.  It  may  be  distinguished  from  ALO8H6  by  its  in- 
solubility in  H4NNaHPO4  bead,  and  readily  separated  from  it  by  fu- 
sion with  KHSO4,  treatment  with  HCl  +  Aq  and  precipitation  of 
AlaO8He  from  the  solution,  if  present,  by  H4NOH  + Aq. 


QUALITATIVE  ANALYSIS.  41 

to  another  portion  add  K4Fe(CN)6  +  Aq,  which  gives 
blue  [FeJ2[Fe(CN)6]3,  or  KCNS  giving  blood  red  solution 
of  Fe2(CNS)6,  if  Fe2  is  present. 

Small  quantities  of  Cr2  may  also  be  detected  by  fus- 
ing the  dried  precipitate  with  a  mixture  of  equal  % parts  of 
Na2CO3  and  KNO3.  If  the  cooled  mass  is  boiled  with 
water,  the  solution  filtered  and  acidified  with  HC2H;iO2, 
on  the  addition  of  Pb(C2H3O2)2  +  Aq,  PbCrO4  is  precipi- 
tated. 

The  filtrate  from  the  BaCO3  precipitate,  which  may 
contain  Zn  and  Mn,  is  heated  to  boiling  and  the  Ba  it 
contains  completely  precipitated  with  dilute  H2SO4 ;  filter 
from  the  BaSO4,  to  the  filtrate  add  NaOH  +  Aq  in  ex- 
cess and  boil.  MnO2H2  is  precipitated,  if  present,  and 
the  solution  may  contain  Zn.  The  precipitate  is  collect- 
ed on  a  filter,  and  a  portion  of  it  fused  on  platinum  wire 
with  Na.2CO3  and  KNO3.  Blue  green  K2MnO4  is  formed, 
if  the  precipitate  was  MnO2H2.  The  NaOH  +  Aq  solu- 
tion, which  may  contain  Zn,  is  acidified  with  HC2H3OS 
and  ZnS,  white,  precipitated  by  H2S,  if  Zn  is  present. 

IfH3PO4and  H2C2O4  are  present,  the  HC1  +Aq  so- 
lution boiled  with  HNO3  and  treated  as  before  must  first 
be  tested  for  Ba,  Sr  and  Ca.  To  a  small  portion  add 
dilute  H2SO4.  If  a  precipitate  is  formed  filter,  and  ex- 
amine in  the  spectroscope.  To  the  filtrate  add  3  times 
its  volume  of  alcohol ;  CaSO4  is  precipitated,'  if  Ca  is 
present,  and  its  presence  may  be  confirmed  by  dissolving 
the  precipitate  in  water  and  throwing  down  CaC2O4  with 
(H4N)2C2O4  +  Aq.  To  the  rest  of  the  solution  add  Fe2Cl6 
+  Aq  cautiously  till  a  drop  of  the  solution  gives  with 
H4NOH  +  Aq  a  yellowish  precipitate.  The  solution  must 


42  LECTURE  NOTES   ON 


then  be  neutralized  with  NajCOg  +  Aq,  as  before,  anc] 
BaCO3  added.  The  precipitate  with  BaCO3  is  examined  as 
above,  except,  of  course,  that  Fe  and  Fe.,  must  be  proved 
present  or  absent  by  H4Fe(CN)6  +  Aq  and  K6Fe2(CN), 
+  Aq,  in  the  original  solution.  The  nitrate  from  the 
BaCO3  precipitate  may  contain  Ca  and  Mg  as  well  as  Mn 
and  Zn.  After  removing  Ba  with  dilute  H.SO4,  H4NOH 
-f  Aq  must  be  added,  ZnS  and  MnS  precipitated,  if  present, 
by  (H4N)2S  +  Aq,  collected  on  a  filter,  and  dissolved  in 
HC1  -f  Aq.  They  may  then  be  separated  and  detected  as 
before.  The  filtrate  from  the  precipitate  of  ZnS  and 
MnS  may  contain  Ca  and  Mg.  The  Ca  is  precipitated 
as  CaC2O4  filtered  off,  and  the  filtrate  tested  for  Mg  by 
adding  NaiHPO4  +  Aq. 

GROUP  H    Ba,  Sr,  Ca,  Mg. 

To  the  filtrate  from  the  general  precipitate  of  Grs. 
III.  and  IV.,  or  to  the  solution  found  not  to  contain 
Grs.  III.-VI.,  add  H4NCl-|-Aq,1  if  it  be  not  already  in 
solution,  then  H4NOH  -f  Aq  in  slight  excess,  unless  the 
solution  is  already  alkaline  ;  heat  almost  to  boiling,  add 
(H4N)2CO3  -I-  Aq  to  complete  precipitation,  and  filter  after 
allowing  it  to  stand  for  a  few  minutes. 

The  filtrate  may  contain  Mg  or  members  of  Gr.  I.  To 
a  small  part  of  it  add  NasHPO4  +  Aq.  A  white  crystalline 
precipitate,  forming  only  after  the  lapse  of  some  time,  if 
the  solution  be  dilute,  is  Mg.XH.N^PO,).,.2  The  rest  of 
the  filtrate  is  then  evaporated  for  Gr.  I. 

1  H4NC1  4-  Aq  prevents  possible  precipitation  of  Mg. 

a  The  nitrate  may  contain  small  quantities  of  Ba,  Sr  or  Ca.  A 
slight  precipitate  with  Na2HPO4  may  therefore  not  be  due  to  pres- 
ence of  Mg.  In  a  fresh  portion  Ba  should  be  tested  for  and  removed 


QUALITATIVE  ANALYSIS.  43 

The  precipitate  thrown  down  by  (H4N)2CO3  4-  Aq 
may  contain  BaCO3,  SrCO:!or  CaCO3,  and  must  be  tested 
for  all  three.  The  carbonates  are  dissolved  in  HC2H3O2, 
and  to  a  small  part  of  the  solution  CaSO4  +  Aq  is  added. 
An  immediate  white  precipitate  is  BaSO4,  and  shows  that 
Ba  is  present,  —  Ca  and  Sr  may  be;  a  tardy  precipitate  is 
SrSO4,  and  shows  that  Ba  is  absent  and  Sr  present,  —  Ca 
may  be  ;  no  precipitate  even  on  long  standing  shows  that 
Ba  and  Sr  are  absent,  and  the  original  precipitate  was 
GaCO3  alone. 

If  Ba  is  present,  it  must  be  removed  before  testing  for 
Sr  or  Ca.  To  the  rest  of  the  HC2H3O2  solution  is  then 
added  K2CrO4  +  Aq  in  slight  excess,  and  the  precipi- 
tated BaCrO4  filtered  off.  To  the  filtrate  add  H4NOH 
+Aq  in  excess,  warm  and  add  (H4N)iCO8+Aq.  The 
precipitate  may  contain  SrCO3  or  CaCO3  or  both.  It 
must  be  washed  till  all  K2CrO4  is  removed  and  dissolved 
in  HC.,H3O2.  To  a  small  portion  of  the  solution  add 
CaSO4-f-Aq.  A  white  precipitate  on  standing  is  SrSO4 
and  shows  Sr  present,  —  Ca  may  be. 

If  Sr  is  present,  to  the  rest  of  the  HC2H3O2  solution, 
from  which  the  Ba  has  been  removed,  or  in  which  it  was 
originally  found  absent,  is  added,  dilute  H2SO4  in  slight 
excess.  After  standing  for  some  time  SrSO4  separates, 
mixed  with  CaSO4,  if  the  solution  is  concentrated  ;  on  fil- 
tering CaSO4  will  be  found  in  solution,  if  present,  by  add- 
ing H4NOH+Aq  in  excess  and  (H4N)2C2O4  +  Aq  ;  Ca 
then  falls  as  white  CaC2O4. 

If  Sr  is  absent,  whether  Ba  was  originally  absent  or  was 


with  dilute  H2SO4,  Ca  with  (H^N^CaO^  +  Aq  before  accepting  the 
precipitate  with  Na2HPO4  +  Aq  as  a  proof  of  the  presence  of  Mg. 


44  LECTURE   NOTES   ON 

removed,  H4NOH  +  Aq  and  (H4N)aCaO4  added  to  the 
rest  of  the  HC2H3O2  solution  precipitates  CaC2O4  if  Ca 
is  present. 

Ba,  Sr  and  Ca  may  also  be  distinguished  by  the  spectro- 
scope. Ba  recognized  by  four  green  bands ;  Sr  by  one 
orange,  two  red,  and  one  blue  band ;  Ca  best  by  a  green 
and  orange  band. 

GROUP  I.    Na,  K,  Li,  HN. 

The  filtrate  from  the  general  precipitate  of  Gr.  II.  or 
the  solution  in  which  Grs.  1 1. -VI.  have  been  found  ab- 
sent, must  be  evaporated  to  dryness  and  ignited  until 
H4N  salts  are  expelled. 

If  Mg  was  found  to  be  absent,  the  residue  contains 
only  Na,  K  or  Li,  and  should  be  tested  with  the  spectro- 
scope. K  gives  a  band  in  the  extreme  red,  Na  a  yellow 
band,  and  Li  a  red  band  between  the  two.  The  presence 
of  Na  in  notable  quantity  is  shown  by  the  intensity  and 
duration  of  the  yellow  flame.  NaHC4H4O6  +  Aq  may 
also  be  used  in  a  cold  concentrated  aqueous  solution  of 
the  residue  as  a  test  for  K,  precipitating  KHC4H4O6. 
NaC2O3  +Aq  precipitates  from  concentrated  solutions 
LiCO3,  or  NaaHPO4  +  Aq,  with  the  addition  of  a  little 
NaOH  -f-Aq,  precipitates  Li3PO4  in  a  solution  not  too 
dilute. 

If  Mg  was  found  present,  the  residue  from  ignition l 
must  be  dissolved  in  a  little  water,  and  BaO2H2  +  Aq 
added  in  slight  excess.  The  MgO.,H2  thus  precipitated 
is  filtered  out,  the  Ba  completely  precipitated  from  the 
boiling  hot  filtrate  by  dilute  H2SO4,  and  the  liquid  freed 

1  MgOoH2  not  precipitated  from  solutions  containing  H4N  salts. 


QUALITATIVE  ANALYSIS.  45 

from  BaSO4  by  filtration  evaporated  to  dryness.  The 
residue,  after  the  excess  of  H2SO4  has  been  driven  off,  is 
tested  as  before  in  the  spectroscope. 

To  test  for  H4N  some  of  the  original  solution  or  sub- 
stance must  be  mixed  with  CaO2H2  to  a  stiff  ^aste,  and 
gently  warmed.  H3N  !  is  then  set  free,  which  may  be  re- 
cognized by  its  action  on  moist  test-paper,  or  by  its  form- 
ing white  fumes  of  H4NC1  with  HC1.2 


DETECTION  OF  ACIDS. 

The  acids  are  divided  into  three  groups,  according  to  the 
solubility  of  the  Ba  and  Ag  salts.3  BaCl2  -f  Aq  precipi- 
tates all  the  members  of  Gr.  I.  in  neutral  or  alkaline  solu- 
tions, but  does  not  precipitate  Grs.  II.  and  III.  AgNO3 
+  Aq  precipitates  in  HNO3  solution  onry  members  of 
Gr.  II.,  but  in  neutral  solution  almost  all  of  Gr.  I. 
Members  of  Gr.  III.  are  precipitated  by  neither  reagent. 
The  acids  are  not  separated  after  precipitation  by  the 
general  reagents,  as  was  the  case  with  bases,  the  presence 
or  absence  of  members  of  the  groups  alone  being  shown. 

In  beginning  the  analysis  for  acids,  those  acids,  which 
from  the  nature  of  the  bases  present  and  the  solvent 
used  are  necessarily  absent,  must  first  be  considered.  In 
a  substance  soluble  in  water  no  acids  can  be  present 
which  form  insoluble  salts  with  any  of  the  bases  found  in 
the  solution.  In  a  substance  insoluble  in  water  and 

1  2H4NC1  +  Ca03H3  =  CaCl  +  2H2O  +  2H3N. 

2  The  HC1  +  Aq  used  must  not  fume  in  the  air. 

3  See  table  of  acids  on  page  19. 


46  LECTURE  NOTES   ON 

soluble  in  acids,  the  number  of  acids  which  may  thus  be 
safely  excluded,  as  forming  soluble  salts  with  the  bases, 
is  small,  and  it  is  better  to  look  for  all.  In  substances 
insoluble  in  water  or  acids,  a  knowledge  of  the  bases 
will  usually  render  the  number  of  acids  that  must  be 
tested  for  very  small. 

If  the  substance  is  soluble  in  water,  the  bases  will 
generally  not  interfere  with  the  detection  of  those  acids 
which  can  be  present,  although  in  testing  for  HC2H3O2 
and  H2C4H4O6  the  solution  cannot  contain  bases  of  Grs. 
III. -VI.  If  the  substance  is  soluble  in  acids  alone,  the 
removal  of  the  bases  of  Grs.  III.-VI.  always  facilitates 
the  detection  of  the  acids,  and  is  often  essential.  They 
should  be  removed  with  HVS,  (H4N).,S  +  Aq,  Na8CO8  + Aq, 
NaOH  +  Aq,  as  the  case  may  be,  any  excess  of  HoS 
removed,  and  the  solution  made  neutral,  carefully  boiling 
out  CO2,  if  Na2CO3  was  used. 

GROUP  I.    1.  M,Cr04,  MnAsOn,  H:,As04,  MsSOs,  M.S.On. 

These  acids  will  have  been  discovered,  if  present,  by 
the  preliminary  examination,  or  in  the  course  of  the  anal- 
ysis for  bases ;  their  presence  must  be  confirmed  by 
special  tests.  They  are  all  decomposed  by  H^S  in  acid 
solution. 

Chromates.— Pb(C2H3O2)2  +  Aq  gives  yellow  PbCrO4, 
insoluble  in  HC2H3O2.  AgNO3  +  Aq  in  neutral  solution 
precipitates  brick  red  AgCrO4. 

Arsenites. — H2S  precipitates  As2S3  yellow  immedi- 
ately from  acid  solutions  ;  AgNO3-fAq  gives  in  neutral 
solutions  pale  yellow  Ag3AsO3.  Further  recognized  in 
presence  of  H3AsO4  by  adding  a  few  drops  of  CuSO4 


QUALITATIVE  ANALYSIS.  47 

+  Aq,  then  NaOH  -f-  Aq  in  excess  ;  on  boiling  Cu2O2H2 
precipitated,  orange  yellow. 

Arseniates. — H2S  precipitates  As.2S3  very  slowly 
from  acid  solutions ;  AgNO3  +  Aq  gives  in  neutral  solu- 
tions red  brown  precipitate  of  Ag3AsO4.  Further  distin- 
guished from  arsenites  by  H4NOH  +  Aq,  H4NC1  -f  Ag, 
and  MgSO4  +  Aq ;  Mg.2(H4N).2(AsO4),  precipitated,  easily 
mistaken  for  phosphate. 

Sulphites. — Salts  give  off  SO2  when  treated  with 
H2SO4  or  HC1  +  Aq.  SO,  recognized  by  smell  and  black- 
ening of  paper  moistened  with  Hg2(NO8)8+-Aq  by  separa- 
tion of  Hg.  Zn  and  HCl  +  Aq  liberate  from  solutions  of 
sulphides  H2  mixed  with  H.2S.  If  sulphides  also  present, 
must  they  be  removed  by  ZnSO4  +  Aq  and  the  filtrate 
tested. 

Hyposulphites. — From  solutions  H2SO4  orHCl  +  Aq 
evolve  SO2  with  separation  of  S.  The  reaction  is  delay- 
ed by  dilution.  Pb(CaH8O2)8  +  Aq  or  AgNO3  +Aq  give 
white  precipitates  which  blacken  on  boiling.1  Sulphides, 
if  present,  must  first  be  removed  with  ZnSO4  +Aq. 

GROUP  I.     2.  (a)  HsPO*,  H3B03,  HCzCh,  HF,  M2C03. 
H<SiO<,  H2C4H408 ;  Ob)  H2S04. 

By  the  preliminary  examination  H2CO3,  H2C4H4O6, 
and  H4SiO4  will  have  been  found,  if  present.  H2CO3 
andH4SiO4  must  be  removed  byHCl+Ag  or  HNO3 
and  evaporation,  if  present  ;  their  presence  is  confirmed 
by  special  tests. 

To  a  solution  free  from  acids  of  Gr.  I.  i,  H2CO3  and 
H4SiO4  add  H4NOH  +  Aq  to  neutral  or  slightly  alkaline 
reaction,  then  BaCl2  +  Aq.  The  precipitate  may  contain 


48  LECTURE  NOTES   ON    . 

the  Ba  salts  of  H3PO4,  H3BO3,  H2C2O4,  HF,  H2C4H4O6 
and  H2SO4.  Add  dilute1  HCi-f  Aq  in  excess;  BaSO4is 
insoluble,  the  other  Ba  salts  dissolve.  If  H4NOH  +  Aq 
is  added  in  excess  to  the  filtered  solution,  Ba3(PO4)2  and 
BaC2O4  are  precipitated,  if  present  ;  the  other  Ba  salts, 
more  or  less  soluble  in  H4NCl-f  Aq,  will  probably  not 
be  precipitated,  if  present  If  therefore  H4NOH  -f-  Aq 
causes  a  precipitate  in  the  HC1  -f  Aq  solution,  special 
tests  must  be  made  for  all  the  acids,  except  H.,SO4, 
whose  presence  or  absence  is  already  established ;  if 
H4NOH  gives  no  precipitate,  H3PO4  and  H2C2O4  are 
absent,  and  for  the  rest  special  tests  must  be  applied. 

It  is  often  advisable  to  add  CaCl2  -f  Aq  to  a  fresh 
portion  of  the  solution  made  slightly  alkaline  with 
H4NOH  +  Aq.  The  Ca  salts  of  H3PO4,  H3BO3, 
H2C2O4,  HFand  H2C4H4Oti  are  thus  precipitated  ;  CaSO4 
is  not  thrown  down,  if  the  solution  is  moderately  dilute. 
Of  these  Ca  salts  CaC2O4  and  CaF2  alone  are  insoluble 
in  HC  H3O2 ;  if  the  precipitate  is  soluble  in  HC.HA,, 
H2C8O4  and  HF  are  absent,  if  insoluble  all  may  be 
present. 

Phosphates. — In  aqueous  solutions  H4NOH  +  Aq, 
H4NC1  -f-  Aq  and  MgSO4  +  Aq  precipitate  crystalline 
Mg2(H4N).2(PO4)2,  which  appears  only  after  some  time,  if 
the  solution  is  dilute.  To  detect  H3PO4  in  salts  soluble 
in  acids  alone,  add  a  little  of  a  HNO3  solution  of  the 
salt  to  (H4N)9MO4  dissolved  in  HNO3;  a  yellow  pre- 
cipitate is  formed  at  once,  or  on  gently  warming  (not 
above  40°),  if  the  solution  is  very  dilute.  H3AsO4  gives 
a  similar  precipitate  on  boiling. 

1  Bad.,  is  insoluble  in  strong  HC1  +  Aq. 


QUALITATIVE   ANALYSIS.  49 

Borates. — Into  a  solution  acid  with  HC1  +  Aq  is 
dipped  a  strip  of  turmeric  paper.  The  paper  when 
dried  at  100°  is  red,  the  red  tint  changing  to  greenish 
black  on  moistening  with  Na2CO3+Aq. 

Oxalates. — Distinguished  from  phosphates  by  the  in- 
solubility of  CaC2O4  in  HC2H3O2,  and  by  giving  no  pre- 
cipitate with  MgSO4  +  Aq  in  presence  of  H4NC1  +  Aq. 
The  salts  heated  with  strong  H2SO4  evolve  CO  and 
CO2.  The  CO  may  be  kindled,  if  in  sufficient  quan- 
tity; dilute  H2SO4  and  MnO2  set  free  CO2.  The  in- 
soluble oxalates  of  Gr.  II.  give,  when  boiled  with  a 
concentrated  solution  of  Na2CO3,  an  insoluble  carbonate 
and  Na2C2O4  in  solution. 

Fluorides. — The  salt  mixed  with  just  .  enough 
strong  H2SO4  to  form  a  thick  paste  is  warmed  in  a 
platinum  crucible  covered  with  a  piece  of  glass.  HF  is 
set  free  and  the  glass  is  etched.  The  etching  is  best 
seen,  if  the  glass  is  covered  with  wax,  and  a  few  scratches 
made  through  it.  If  Si  is  present,  SiF4  is  'evolved. 
Compounds  of  F,  upon  which  H2SO4  has  no  action,  must 
be  fused  with  a  mixed  Na2CO3  and  K2CO3,  CaF2  precipi- 
tated, and  tested  as  before. 

Tartrates. — The  presence  of  tartrates  is  first  recog- 
nized in  the  preliminary  examination  by  charring  with 
odor  of  burnt  sugar.  CaC4H6O6  is  distinguished  by  its 
dissolving  in  cold  NaOH  +  Aq ;  when  the  solution  is 
boiled  the  salt  is  thrown  down  as  a  gelatinous  precipitate, 
which  redissolves  as  the  solution  cools.  In  a  solution 
acid  with  HC2H3O2,  KC,H3O2  precipitates  KHC4H4O6. 

Carbonates. — Salts  decomposed  by  acids  with  effer- 
vescence,   the   escaping   CO3  precipitates    CaCO3  from 
3 


SO  LECTURE  NOTES   ON 

CaO2H2  +  Aq.  HC1  +  Aq  is  poured  upon  the  carbon- 
ate in  a  test  tube,  the  gas  allowed  to  collect  and  care- 
fully decanted  into  another  tube  half  full  of  Ca2O2H2 
+  Aq.  An  excess  of  CO2  dissolves  CaCO3  forming  solu- 
ble CaH2(CO3)2. 

Silicates.  —  Generally  recognized  by  the  separation 
of  gelatinous  H4SiO4  on  adding  HC1  +  Aq.  A  solution 
of  a  silicate  acidified  with  HC1  +  Aq  and  evaporated  to 
dryness  leaves  all  its  Si  as  a  hard  gritty  powder  insoluble 
in  water  or  HC1  +  Aq.  The  powder  is  also  insoluble 
in  a  bead  of  NaH4NHPO4  ;  A12O3  dissolves  readily. 

Sulphates.  —  Sufficiently  characterized  by  BaSO4  : 
insoluble  in  dilute  HC1  +  Aq.  Ignited  on  charcoal 
with  Na2CO3,  in  the  inner  blowpipe  flame,  Na2S  is  formed, 
which,  when  moistened  with  water,  stains  Ag  black. 

GROUP  II.      HC1,   HBr,    HI,   HCN,    ILS,    H<Fe(CN)8, 


The  presence  of  H2S  will  have  been  already  estab- 
lished, and  probably  that  of  HC1,  HBr,  HI  and  HCN. 
H2S,  if  present,  must  be  expelled.  As  the  Ag  salts  of  all 
the  acids  of  Gr.  I.  except  AgF  are  insoluble  in  water 
and  soluble  in  HNO3,  acidify  the  solution  with  HNO3 
and  add  AgNO3  +  Aq.  The  precipitate  may  contain 
Ag  salts  of  all  the  members  of  the  .group.  They  are 
soluble  in  H4NOH  +  Aq,  except  Agl  and  Ag4Fe(CN)e. 
Further  than  this  special  tests  must'  be  made. 

Chlorides.—  On  heating  with  H2SO4  and  MnO2  C12 
evolved,  recognized  by  color,  odor  and  bleaching  power. 
HC1  in  the  presence  of  HBr  and  HI  may  be  recognized 
by  adding  to  the  hot  solution  AgNO3  +  Aq  in  quantity 


QUALITATIVE  ANALYSIS.  51 

insufficient  to  cause  complete  precipitation.  If  the  fil- 
tered solution  no  longer  contains  HI  or  HBr,  and  AgNO3 
+  Aq  causes  a  further  precipitate,  HC1  is  present,  since 
AgCl  is  last  thrown  down. 

Bromides. — On  heating  with  H2SO4  and  MnO2  Br2 
is  evolved.  To  a  solution  of  a  bromide  in  a  test  tube  add 
a  little  CS2  or  chloroform,  then  Cl2-}-Aq  drop  by  drop, 
shaking  the  tube  ;  the  liberated  Br2  dissolves  in  the  CS2 
coloring  it  red.  If  HI  is  also  present  the  CS2  is  violet. 
Add  then  Cl2+Aq,  cautiously  shaking  the  tube,  and  the 
violet  I2  color  will  gradually  disappear,  and  leave  the  CS2 
colored  red  by  Br2 — more  C12  Aq  will  bleach  the  Br2 
color  also. 

Iodides. — To  a  neutral  or  slightly  acid  solution  of  an 
iodide  add  a  little  thin  boiled  starch  paste,  and  then  C12 
-fAq  cautiously.  A  blue  compound  of  I  with  starch  is 
formed.  The  color  fades  with  heat  or  with  an  excess  of 
Cl2  +  Aq.  Instead  of  CL  +  Aq,  KNO2  + Aq,  in  a  solution 
acid  with  H2SO4,  may  be  used  to  advantage,  as  an  ex 
cess  does  little  harm. 

Cyanides. — Free  HCN  liberated  from  cyanides  may 
be  recognized  by  its  odor  (vapors  poisonous).  If  a  few 
drops  of  yellow  (H4N);jS+ Aq  be  exposed  to  the  vapors  of 
HCN  or  added  to  a  liquid  containing  HCN,  H4NCNS  is 
formed.  The  (H4N)2S-|-Aqor  the  solution  is  evaporated 
until  the  excess  of  (H4N)2S  is  driven  off  (not  heated  above 
100°),  dilute  HCl  +  Aq  added  and  blood  red  Fe,(CNS)6 
formed  in  solution  by  adding  Fe2Cl6  +  Aq.  To  a  solution 
of  HCN,  or  a  cyanide,  add  successively  Fe4SO+Aq, 
Fe2Cl6  +  Aq,  NaOH  +  Aq  and  HCl  +  Aq  in  excess; 
there  is  formed  blue  insoluble  [Fe2]2[Fe(CN)6J3. 


52  LECTURE  NOTES   ON 

Sulphides.  —  H,S  is  liberated  by  HC1  -f  Aq  from 
those  sulphides  which  are  decomposed  by  it  Paper 
moistened  with  Pb(C2H3O2)2  +  Aq,  best  slightly  alkaline, 
is  blackened  by  exposure  to  H^S,  PbS  formed.  From 
those  sulphides  not  attacked  by  HC1  +  Aq,  HNO3  or 
HC1  4-  Aq  and  HNO3  separate  S,  which  is  yellow  and  often 
spongy,  and  burns  to  SOj.  More  or  less  H2SO4  also 
formed. 

Ferrocyanides.—  Soluble  salts  recognized  by  giv- 
ing on  addition  of  Fe2Cl6H-Aq,  blue  [FeJ9[Fe(CN)J3. 
Insoluble  salts  boiled  with  NaOH  -f  Aq  and  the  acidified 
solution  tested  with  Fe2Ci6  -j-  Aq. 

Ferrocyanides.  —  Soluble  salts,  recognized  by  add- 
ing FeSO4  -f  Aq—  best  made  from  dilute  H2SO4  and 
Fe  to  insure  absence  of  Fe2  salt.  Blue  Fe3Fe2(CN)12 
formed.  Insoluble  salts  treated  like  the  insoluble  ferro- 
cyanides,  and  the  solution  tested  with  FeSO4  -j-  Aq. 


GROUP  IH    HN03,  HC103,  HC»H3<k 

The  acids  will  have  been  recognized  in  the  preliminary 
examination  ;  to  confirm  their  presence  special  tests  must 
be  made. 

Nitrates.  —  Treated  with  strong  H2SO4  and  Cu 
turnings  give  off  NO,  which  forms  orange  red  NO2  with 
air.  A  better  test  is  to  mix  in  a  test  tube  with  a  concen- 
trated solution  of  FeSO4,  Add  strong  H2SO4  in  the  cold, 
letting  it  run  down  the  side  of  the  tube  and  collect  at  the 
bottom  ;  where  the  two  layers  are  in  contact,  a  brown  or 
black  ring  is  formed. 

Chlorates.  —  HC1  +  Aq  or  H2SO4  decompose  all 
salts,  giving  yellow  solution  and  yellow  green  gas. 


QUALITATIVE   ANALYSIS.  53 

Acetates. — H2SO4  liberates  HC2H3O.;,  which  may 
be  recognized  by  its  odor.  A  neutral  solution  of  an 
acetate,  on  the  addition  in  the  cold  of  a  few  drops  of 
Fe,,Cl6,  turns  red  from  the  formation  of  Fe-,(C2H3O.,)6.  On 
boiling  the  red  solution,  a  brown  basic  salt  is  thrown  down 
and  the  liquid  above  is  colorless.  Before  applying  this 
test,  the  bases  of  Grs.  III.— VI.  must  be  removed,  and  the 
solution  made  strictly  neutral. 


S^a^jpcn.o^.jj.r,,* 

to                                                       *oio     h- 

CO                                                                              COOS       » 

to 

HoS 

CO 

_l             ^    »a_l 

HC1 

w                 to     Ascc08^ 

HBr 

T                     V 

HI. 

f  f      f  .     .          f* 

HCN. 

tO:     tO  »0  >-  <0  tO  tO  is  tO  tO  10  V  •-  :     l-*to:     Mtol»M»1»*M 

H2CrO4. 

W:     :     :     tO:     tOtOtOlOtOtOto'-     tOtO-     •     tOtOtOtO>-'i-'>-i 

H3As03. 

H3A804. 

k-itO^                                     "^              - 

H  SO 

to     to                       M 

H3P04. 

:  :  ^Etoto:  :  tototo^totototototoSto^K,  —  ^ 

H3B03. 

h-l                     h-l 

H2C20.. 

^a              t-i                    i-i^i-ii-i                    Jp>OtOtO 

HF1. 

•    :    :    to  to  to  to  to  to  to  to  to  to  to  t*  :    :    •    to  to  »o  to  '-'  i-»  *+ 

H2C03. 

V 

•    •    '•    toto-    •    •    to-    tototototototocototowto-    MI-I 

H4SiO4. 

to:   ^E^totoEtoto^toEtoE-^^E^^toMM^ 

H2C4H400. 

f                      T1 

•    coco-    w-    •    •    tocococotoioosco-    •    t-i  i-*  »-i  to  M  i-»  i-«. 

H4Fe(CN)e. 

:  :   co:  :  :  •  •'  »o  co  co  w  co  to  co  i-i  :  :  >-'>-»:  :  h-n-ih* 

H8Fe(2CN)12. 

HNO3. 

. 

HClOg. 

HC2H302. 


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BERKELEY 

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MAR  1670 -12AM 


4 


LD  21-100m-9,'47(A5702sl6)476 


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l8mo,  cloth,  $1.00. 

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4.  HALF-HOURS  WITH  THE  TELES7/ 
Guide  to  the  Use  of  the  Telescope 
Instruction.     Adapted    to   inexpe/ 
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HALF-HOURS  WITlX 
to  the  Knowledge  ^ 
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